Lamp temperature detection circuit and detection method based on level comparison conversion

Abstract

The invention discloses a lamp temperature detection circuit and detection method based on level comparison conversion. The circuit comprises a control unit, a driving signal processing module, a power supply module, an LED driving module, a light source module and a level comparison conversion circuit. The method comprises the following steps: acquiring a PWM control signal, performing level matching and driving processing, and outputting the preprocessed PWM control signal; carrying out constant-current driving and constant-voltage driving on the preprocessed PWM control signal, and outputting a PWM-form current; controlling the light source module to work according to the PWM form current, and outputting a feedback temperature level signal of the work of the light source module through the NTC thermistor unit; temperature judgment is carried out according to the feedback temperature level signal, and the control unit is controlled to work according to a temperature judgment result. According to the embodiment, the lamp can be automatically extinguished when the temperature is abnormal, and the lamp is prevented from being damaged. The method can be widely applied to the technical field of lamp control.

Description

Technical Field

[0001] This application relates to the technical field of lamp control, and particularly to a lamp temperature detection circuit and detection method based on level comparison and conversion. Background Art

[0002] Currently, the cooling of the LED light source module is based on the real-time temperature signal fed back by the module. Through the fan heat dissipation control system, the heat dissipation mechanism of the light source module is dynamically cooled by blowing air, so as to control the internal temperature of the lamp within a certain safe range. This temperature signal is generally a voltage value, so analog voltage detection-related components or control chips are required. However, there are often a certain proportion of defective chips in these devices, or they are damaged due to reasons such as static electricity during use. It is possible that the actual temperature of the lamp is already quite high. Due to device damage, the detection is abnormal, and the displayed temperature is still low. The fan heat dissipation system does not start or operates at low power. At this time, the internal temperature of the lamp will continue to rise. In the long run, in the lightest case, the light flux of the lamp will be severely attenuated. In the worst case, the extremely high temperature inside the lamp will instantly burn out and catch fire, causing safety accidents. The relevant solution technology is to add an external PTC, place it on the radiator, and connect it in series on the power line of the control board. When the temperature reaches a certain level, the PTC will disconnect, causing the control board to directly lose power, and then the LED light source module will go out. However, it requires changing the structure, increasing the cost, and there is no any prompting measure for the lamp direct power-off system, making it difficult for maintenance personnel to judge the reason for the abnormal power-off.

[0003] In summary, the technical problems existing in the related technologies need to be improved. Summary of the Invention

[0004] The main purpose of the embodiments of this application is to propose a lamp temperature detection circuit and detection method based on level comparison and conversion, which can realize the automatic extinguishing of the lamp when the temperature is abnormal and avoid lamp damage.

[0005] To achieve the above object, on the one hand, an embodiment of the present application proposes a lamp temperature detection circuit based on level comparison conversion. The circuit includes a control unit, a drive signal processing module, a power supply module, an LED drive module, a light source module, and a level comparison conversion circuit. The light source module includes an NTC thermistor unit. The first output terminal of the power supply module is connected to the first input terminal of the control unit. The second output terminal of the power supply module is connected to the first input terminal of the drive signal processing module. The output terminal of the control unit is connected to the second input terminal of the drive signal processing module. The output terminal of the drive signal processing module is connected to the input terminal of the LED drive module. The output terminal of the LED drive module is connected to the input terminal of the light source module. The first output terminal of the light source module is connected to the second input terminal of the control unit. The second output terminal of the light source module is connected to the input terminal of the level comparison conversion circuit. The output terminal of the level comparison conversion circuit is connected to the third input terminal of the control unit, where:

[0006] The power supply module is used to provide power signals for the control unit and the drive signal processing module;

[0007] The control unit is used to output a PWM control signal according to a control instruction;

[0008] The drive signal processing module is used to perform level matching and drive processing on the PWM control signal and output a preprocessed PWM control signal;

[0009] The LED drive module is used to obtain the preprocessed PWM control signal for constant current drive and constant voltage drive and output a PWM-form current;

[0010] The light source module is used to receive the PWM-form current for lighting and output a feedback temperature level signal through the NTC thermistor unit;

[0011] The level comparison conversion circuit is used to perform temperature judgment according to the feedback temperature level signal and control the operation of the control unit according to the temperature judgment result.

[0012] In some embodiments, the NTC thermistor unit includes a first resistor and an NTC unit. The first end of the first resistor is connected to a high-level signal. The second end of the first resistor is connected to the first pin of the NTC unit and obtains the feedback temperature level signal. The second pin of the NTC unit is grounded.

[0013] In some embodiments, the level comparison and conversion circuit includes a first operational amplifier, a second operational amplifier, a second resistor, a third resistor, a fourth resistor, a fifth resistor, and a thermistor. Wherein, the first end of the second resistor is connected to a high-level signal, the first end of the third resistor is grounded, the second end of the second resistor, the second end of the third resistor, and the negative input terminal of the first operational amplifier are connected. The positive input terminal of the first operational amplifier is connected to the negative input terminal of the second operational amplifier to obtain the feedback temperature level signal. The first end of the fourth resistor is grounded, the first end of the fifth resistor is connected to a high-level signal, the second end of the fourth resistor, the second end of the fifth resistor, and the positive input terminal of the first operational amplifier are connected. The control terminal of the first operational amplifier is connected to the first end of the thermistor and is connected to a high-level signal, the control terminal of the second operational amplifier is grounded, and the output terminals of the first operational amplifier and the second operational amplifier are connected to the second end of the thermistor.

[0014] In some embodiments, it further includes a power-on and power-off circuit for the drive signal processing module. The input terminal of the power-on and power-off circuit for the drive signal processing module is connected to the output terminal of the level comparison and conversion circuit, and the output terminal of the power-on and power-off circuit for the drive signal processing module is connected to the input terminal of the drive signal processing module. The power-on and power-off circuit for the drive signal processing module is used to control the power-on and power-off of the drive signal processing module according to the temperature judgment result.

[0015] In some embodiments, the power-on and power-off circuit for the drive signal processing module includes a first MOS transistor, a second MOS transistor, a first diode, a sixth resistor, and a seventh resistor. Wherein, the source electrode of the second MOS transistor is connected to the first end of the seventh resistor and is connected to a first high-level signal, the drain electrode of the second MOS transistor is connected to a second high-level signal, the gate electrode of the second MOS transistor, the second end of the seventh resistor, and the drain electrode of the first MOS transistor are connected. The positive terminal of the first diode is connected to the output terminal of the level comparison and conversion circuit, the negative terminal of the first diode, the gate electrode of the first MOS transistor, and the first end of the sixth resistor are connected, and the second end of the sixth resistor and the source electrode of the first MOS transistor are both grounded.

[0016] In some embodiments, it further includes an AND gate circuit module. The first input terminal of the AND gate circuit module is connected to the output terminal of the level comparison and conversion circuit, the second input terminal of the AND gate circuit module is connected to the output terminal of the control unit, and the output terminal of the AND gate circuit module is connected to the input terminal of the drive signal processing module. Wherein, the AND gate circuit module is used to perform an AND operation on the temperature judgment result and the PWM control signal to control the operation of the light source module.

[0017] In some embodiments, the AND gate circuit module includes an eighth resistor, a ninth resistor, a tenth resistor, a third MOS transistor, and a fourth MOS transistor. Among them, the first ends of the eighth resistor and the tenth resistor are both connected to a high-level signal, the first end of the ninth resistor is connected to the PWM control signal, the gate of the fourth MOS transistor is connected to the temperature judgment result, the second ends of the eighth resistor, the second end of the ninth resistor, and the drain of the third MOS transistor are connected and output a control signal, the second end of the tenth resistor, the gate of the third MOS transistor, and the drain of the fourth MOS transistor are connected, and the sources of the third MOS transistor and the fourth MOS transistor are both grounded.

[0018] To achieve the above object, on the other hand, an embodiment of the present application proposes a detection method for a lamp temperature detection circuit based on level comparison and conversion. The method includes the following steps:

[0019] Obtain the PWM control signal, perform level matching and driving processing, and output the preprocessed PWM control signal;

[0020] Perform constant current driving and constant voltage driving on the preprocessed PWM control signal, and output a PWM-form current;

[0021] Control the light source module to work according to the PWM-form current, and output a feedback temperature level signal of the light source module through the NTC thermistor unit;

[0022] Perform temperature judgment according to the feedback temperature level signal, and control the operation of the control unit according to the temperature judgment result.

[0023] In some embodiments, the performing temperature judgment according to the feedback temperature level signal and controlling the operation of the control unit according to the temperature judgment result includes:

[0024] Determine a first threshold voltage and a second threshold voltage according to the resistance value of the level comparison and conversion circuit;

[0025] Determine the lowest operating temperature and the highest operating temperature according to the allowable operating temperature range of the light source module;

[0026] Determine the corresponding thermistor value according to the lowest operating temperature and the highest operating temperature;

[0027] Combine the NTC thermistor unit and the thermistor value to perform voltage conversion calculation to obtain the voltage value of the feedback temperature level signal;

[0028] If the voltage value of the feedback temperature level signal is between the first threshold voltage and the second threshold voltage, output a high-level voltage control signal; otherwise, output a low-level voltage control signal.

[0029] The high-level voltage control signal controls the control unit to continue outputting the PWM control signal, and the low-level voltage control signal controls the control unit to stop outputting the PWM control signal, thereby realizing the control of the operation of the control unit.

[0030] In some embodiments, it further includes:

[0031] If the output of the level comparison and conversion circuit is the high-level voltage control signal, the power supply of the drive signal processing module is kept connected through the power supply on / off circuit of the drive signal processing module;

[0032] If the output of the level comparison and conversion circuit is the low-level voltage control signal, the power supply of the drive signal processing module is disconnected through the power supply on / off circuit of the drive signal processing module;

[0033] Or;

[0034] If the output of the level comparison and conversion circuit is the high-level voltage control signal, an AND operation is performed with the PWM control signal through the AND gate circuit module, and the operation result controls the normal operation of the light source module;

[0035] If the output of the level comparison and conversion circuit is the low-level voltage control signal, an AND operation is performed with the PWM control signal through the AND gate circuit module, and the operation result controls the light source module to stop working.

[0036] The embodiments of the present application at least include the following beneficial effects: The present application provides a lamp temperature detection circuit and detection method based on level comparison and conversion. This solution controls the operation of the light source module by obtaining the PWM control signal, performing level matching and drive processing, and performing constant current drive and constant voltage drive, and outputs a feedback temperature level signal, that is, a real-time temperature signal, of the operation of the light source module through the NTC thermistor unit, performs temperature judgment, and converts it into two temperature thresholds to output high or low levels, converting linear temperature data into simple high and low levels, and can realize automatic extinguishing of the lamp when the temperature is abnormal, avoiding damage to the lamp. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 is a schematic structural diagram of a lamp temperature detection circuit based on level comparison and conversion provided by an embodiment of the present application;

[0038] Figure 2 is a schematic step flow diagram of a detection method of a lamp temperature detection circuit based on level comparison and conversion provided by an embodiment of the present application;

[0039] Figure 3 is a schematic hardware framework diagram of the control and drive of an existing lamp light source module provided by an embodiment of the present application;

[0040] Figure 4 It is a schematic diagram of a lamp temperature detection circuit with a power on / off circuit for a signal processing module provided by an embodiment of the present application;

[0041] Figure 5 It is a schematic diagram of a lamp temperature detection circuit with an AND gate circuit module provided by an embodiment of the present application;

[0042] Figure 6 It is a schematic diagram of the principle of a level comparator circuit provided by an embodiment of the present application;

[0043] Figure 7 It is a schematic diagram of the input / output voltage characteristics of a level comparator circuit provided by an embodiment of the present application;

[0044] Figure 8 It is a schematic diagram of the circuit principle of an NTC thermistor unit provided by an embodiment of the present application;

[0045] Figure 9 It is a schematic diagram of the temperature-voltage relationship of an NTC thermistor unit provided by an embodiment of the present application;

[0046] Figure 10 It is a schematic diagram of the principle of a power on / off circuit for a signal processing module provided by an embodiment of the present application;

[0047] Figure 11 It is a schematic diagram of the principle of an AND gate circuit module provided by an embodiment of the present application;

[0048] Figure 12 It is a schematic diagram of the AND gate principle using an AND gate chip component provided by an embodiment of the present application;

[0049] Figure 13 It is a schematic diagram of the process of signal monitoring for a level conversion circuit provided by an embodiment of the present application. Detailed implementation manners

[0050] In order to make the objectives, technical solutions and advantages of the present application more clear and understandable, the present application will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application. When the following description relates to the accompanying drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The implementation manners described in the following exemplary embodiments do not represent all implementation manners consistent with the embodiments of the present application. They are only examples of systems and methods that are consistent with some aspects of the embodiments of the present application as detailed in the appended claims.

[0051] It can be understood that the terms "first", "second", etc. used in this application may be used in the embodiments of the present invention to describe various concepts. However, unless otherwise specified, these concepts are not limited by these terms. These terms are only used to distinguish one concept from another. For example, without departing from the scope of the embodiments of this application, the first information may also be referred to as the second information. Similarly, the second information may also be referred to as the first information. Depending on the context, words such as "if" and "when" used herein may be interpreted as "when...", "while...", or "in response to determining".

[0052] The terms "at least one", "multiple", "each", "any one", etc. used in this application, at least one includes one, two or more than two, multiple includes two or more than two, each refers to each of the corresponding multiple, and any one refers to any one of the multiple.

[0053] Unless otherwise defined, all technical and scientific terms used in the embodiments of the present invention have the same meaning as commonly understood by those skilled in the technical field to which this application belongs. The terms used in the embodiments of the present invention are only for the purpose of describing the embodiments of this application and are not intended to limit this application.

[0054] First of all, it should be noted that as Figure 3 shown, the existing control unit is responsible for receiving the level signal fed back by the light source module NTC. The control unit judges whether the level is within the normal range, that is, the normal temperature range. If the temperature is within the normal range, the control unit outputs the corresponding PWM control signal to the drive signal processing module according to the control instruction, and then controls the LED drive module. The LED drive module outputs to drive the light source module, and this process repeats to form a closed loop. The problem is that the control unit is a hardware device, and there will be a certain proportion of defective chips. Once the ADC analog-to-digital detection and conversion unit of the control unit is abnormal and cannot correctly reflect the real temperature, for example, if the actual temperature of the light source module has reached 100 degrees Celsius, but the ADC analog-to-digital detection and conversion unit of the control unit reads the temperature as 30 degrees Celsius, which has not reached the 75 degrees Celsius that the control unit wants to control, the control unit will not take measures to reduce the function or turn off the light, and the temperature inside the lamp body will continue to rise. When it rises above 300 degrees Celsius, there is a risk of fire.

[0055] Based on this, in the embodiments of the present invention, a hardware device for level comparison and conversion is added. The NTC signal fed back by the light source module is connected to this hardware device as an input. This hardware device monitors the NTC signal fed back by the light source module, that is, the real-time temperature signal, which is an analog quantity. By setting the voltage threshold of the hardware device, one voltage threshold corresponds to one abnormal temperature, and a maximum temperature and a minimum temperature are set. The hardware device outputs a high level within the set temperature range, and outputs a low level in other temperature cases. Then, using this signal that can monitor the flipped level and connecting it to a group of logic control devices, when the level is high, the lamp can be lit, and when the level is low, the lamp cannot be lit, thereby protecting the lamp from automatically extinguishing when an abnormal temperature occurs and avoiding safety accidents such as high-temperature fires of the lamp.

[0056] Referring to Figure 1 , Figure 1 FIG. is a schematic structural diagram of a lamp temperature detection circuit based on level comparison and conversion provided by an embodiment of the present invention. Referring to Figure 1 , the circuit includes a control unit, a drive signal processing module, a power supply module, an LED drive module, a light source module, and a level comparison and conversion circuit. The light source module includes an NTC thermistor unit. The first output terminal of the power supply module is connected to the first input terminal of the control unit, the second output terminal of the power supply module is connected to the first input terminal of the drive signal processing module, the output terminal of the control unit is connected to the second input terminal of the drive signal processing module, the output terminal of the drive signal processing module is connected to the input terminal of the LED drive module, the output terminal of the LED drive module is connected to the input terminal of the light source module, the first output terminal of the light source module is connected to the second input terminal of the control unit, the second output terminal of the light source module is connected to the input terminal of the level comparison and conversion circuit, and the output terminal of the level comparison and conversion circuit is connected to the third input terminal of the control unit, where:

[0057] The power supply module is used to provide power signals for the control unit and the drive signal processing module;

[0058] Specifically, the power supply module only refers to the unit that provides electrical energy for the control unit and the drive signal processing module, that is, the low-voltage power supply module of the logic circuit.

[0059] The control unit is used to output a PWM control signal according to a control instruction;

[0060] Specifically, the control unit includes an MCU, a CPU, a DSP, a programmable logic device, etc. It has a PWM output control function unit, an ADC analog-to-digital detection and conversion unit, and a general I / O port. The PWM output is used to provide control signals for the drive signal processing module and the LED drive module to achieve control of the power of the light source module, which is the most mainstream dimming method at present. The ADC analog-to-digital detection and conversion unit is used to receive the feedback signal of the NTC thermistor inside the light source module, which reflects the temperature information.

[0061] The drive signal processing module is used to perform level matching and drive processing on the PWM control signal and output the preprocessed PWM control signal;

[0062] Specifically, the drive signal processing module performs functions of level matching, enhancing drive capability, and increasing anti-interference capability on the PWM signal output by the control unit; the processed PWM signal is sent to the LED drive module for dimming control.

[0063] The LED drive module is used to obtain the preprocessed PWM control signal for constant current drive and constant voltage drive and output a PWM-form current;

[0064] Specifically, the LED drive module uses PWM for constant current drive or constant voltage drive; its function is to output a PWM-form current according to the PWM signals received from the control unit and the drive signal processing module for driving the light source module to emit light.

[0065] The light source module is used to receive the PWM-form current to emit light and output a feedback temperature level signal through the NTC thermistor unit;

[0066] Specifically, the light source module is equipped with a self-designed light source board and an off-the-shelf module with monitoring components such as NTC for emitting light. The internal NTC outputs a level linearly related to the temperature according to the module temperature; the level of this NTC is connected to the ADC analog-to-digital detection and conversion unit of the control unit.

[0067] Among them, as Figure 8 shown, the NTC thermistor unit includes a first resistor R1 and an NTC unit. The first end of the first resistor is connected to a high-level signal, the second end of the first resistor is connected to the first pin of the NTC unit to obtain the feedback temperature level signal, and the second pin of the NTC unit is grounded.

[0068] The level comparison and conversion circuit is used to judge the temperature according to the feedback temperature level signal and control the operation of the control unit according to the temperature judgment result.

[0069] Specifically, as Figure 6As shown, the level comparison and conversion circuit includes a first operational amplifier U1, a second operational amplifier U2, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, and a thermistor Rs. Among them, the first end of the second resistor is connected to a high-level signal, the first end of the third resistor is grounded, the second ends of the second resistor and the third resistor are connected to the negative input terminal of the first operational amplifier, the positive input terminal of the first operational amplifier is connected to the negative input terminal of the second operational amplifier and obtains a feedback temperature level signal, the first end of the fourth resistor is grounded, the first end of the fifth resistor is connected to a high-level signal, the second ends of the fourth resistor and the fifth resistor are connected to the positive input terminal of the first operational amplifier, the control terminal of the first operational amplifier is connected to the first end of the thermistor and is connected to a high-level signal, the control terminal of the second operational amplifier is grounded, and the output terminals of the first operational amplifier and the second operational amplifier are connected to the second end of the thermistor.

[0070] In this embodiment, the level comparison and conversion circuit is composed of a circuit such as a dual-limit comparator (also known as a window comparator). This circuit can flip the output level according to whether the level of the input analog signal is between two specified levels, and through calculation, convert it into two temperature thresholds to output high or low levels; this circuit is used to automatically identify whether the temperature is abnormal, convert linear temperature data into simple high and low levels, which is convenient for the application of subsequent circuits; this circuit can be connected to the I / O port of the control unit, the power-off and on circuit of the drive signal processing module, and the AND gate circuit module.

[0071] Furthermore, it should be noted that as Figure 4 shown, it further includes a power-off and on circuit of the drive signal processing module. The input terminal of the power-off and on circuit of the drive signal processing module is connected to the output terminal of the level comparison and conversion circuit, and the output terminal of the power-off and on circuit of the drive signal processing module is connected to the input terminal of the drive signal processing module. The power-off and on circuit of the drive signal processing module is used to control the power-off and on of the drive signal processing module according to the temperature judgment result.

[0072] Specifically, as Figure 10 shown, the power-off and on circuit of the drive signal processing module includes a first MOS transistor Q1, a second MOS transistor Q2, a first diode D1, a sixth resistor R6, and a seventh resistor R7. Among them, the source electrode of the second MOS transistor is connected to the first end of the seventh resistor and is connected to a first high-level signal, the drain electrode of the second MOS transistor is connected to a second high-level signal, the gate electrode of the second MOS transistor and the second end of the seventh resistor are connected to the drain electrode of the first MOS transistor, the positive terminal of the first diode is connected to the output terminal of the level comparison and conversion circuit, the negative terminal of the first diode, the gate electrode of the first MOS transistor, and the first end of the sixth resistor are connected, and the second end of the sixth resistor and the source electrode of the first MOS transistor are both grounded.

[0073] In this embodiment, the power on / off circuit of the drive signal processing module is connected in series on the power line of the drive signal processing module, and the high or low level output by the level comparison and conversion circuit is used to control the power on or off of the drive signal processing module, achieving the function of allowing or prohibiting operation.

[0074] Furthermore, it should be noted that, as Figure 5 shown, it further includes an AND gate circuit module. The first input terminal of the AND gate circuit module is connected to the output terminal of the level comparison and conversion circuit, the second input terminal of the AND gate circuit module is connected to the output terminal of the control unit, and the output terminal of the AND gate circuit module is connected to the input terminal of the drive signal processing module. Among them, the AND gate circuit module is used to perform an AND operation on the temperature judgment result and the PWM control signal to control the operation of the light source module.

[0075] Specifically, as Figure 11 shown, the AND gate circuit module includes an eighth resistor R8, a ninth resistor R9, a tenth resistor R10, a third MOS transistor Q3, and a fourth MOS transistor Q4. Among them, the first ends of the eighth resistor and the tenth resistor are both connected to a high-level signal, the first end of the ninth resistor is connected to the PWM control signal, the gate of the fourth MOS transistor is connected to the temperature judgment result, the second ends of the eighth resistor, the second end of the ninth resistor, and the drain of the third MOS transistor are connected and output a control signal, the second end of the tenth resistor, the gate of the third MOS transistor, and the drain of the fourth MOS transistor are connected, and the sources of the third MOS transistor and the fourth MOS transistor are both grounded.

[0076] In this embodiment, the AND gate circuit module includes a diode, a relay, an AND gate chip, etc. to form a logical AND gate circuit. Its function is to perform a logical AND operation on the PWM signal of the control unit and the signal of the level comparison and conversion circuit. Only when the signal of the level comparison and conversion circuit is high can the PWM signal be normally output. When the signal of the level comparison and conversion circuit is low, the PWM signal cannot be output.

[0077] Please refer to Figure 2 , this application embodiment also provides a detection method for a lamp temperature detection circuit based on level comparison and conversion, which is applied to the above-mentioned lamp temperature detection circuit. The method includes:

[0078] S100. Obtain the PWM control signal, perform level matching and drive processing, and output the preprocessed PWM control signal;

[0079] S200. Perform constant current drive and constant voltage drive on the preprocessed PWM control signal, and output a PWM-form current;

[0080] S300. Control the operation of the light source module according to the PWM-form current, and output a feedback temperature level signal of the operation of the light source module through the NTC thermistor unit;

[0081] S400. Judge the temperature according to the feedback temperature level signal, and control the operation of the control unit according to the temperature judgment result;

[0082] It should be noted that in some embodiments, step S400 may include: S410. Determine the first threshold voltage and the second threshold voltage according to the resistance value of the level comparison conversion circuit; S420. Determine the minimum operating temperature and the maximum operating temperature according to the allowable operating temperature range of the light source module; S430. Determine the corresponding thermistor resistance value according to the minimum operating temperature and the maximum operating temperature; S440. Combine the NTC thermistor unit and the thermistor resistance value to perform voltage conversion calculation to obtain the voltage value of the feedback temperature level signal; S450. If the voltage value of the feedback temperature level signal is between the first threshold voltage and the second threshold voltage, output a high-level voltage control signal, otherwise, output a low-level voltage control signal; S460. The high-level voltage control signal controls the control unit to continue to output the PWM control signal, and the low-level voltage control signal controls the control unit to stop outputting the PWM control signal, so as to control the operation of the control unit.

[0083] In some specific embodiments, the level comparison conversion circuit is a circuit composed of a dual-limit comparator (also known as a window comparator), etc. The circuit can be composed of two LM339 or other operational amplifiers and several resistors. When the signal voltage U to be compared in is between the threshold voltages U1 and U2, the output level U o is high U oH , otherwise, the output level U o is high U oL . As Figure 7 shown, it is the input-output characteristic diagram of the level comparison conversion circuit.

[0084] First, set the threshold voltages U1 and U2 and the circuit parameters, evaluate the temperature range, and the minimum allowable operating temperature of the product, which is assumed to be -20 °C and denoted as T1; check the maximum temperature limit provided by the light source module, which is assumed to be 75 °C. On this basis, increase the high temperature by 10 °C as the limit, denoted as T2. The temperature range is -20 °C to 85 °C, and corresponding forced light-off measures are taken as the limit temperature when the chip bad die software detection fails.

[0085] Further refer to the NTC temperature-resistance table of the thermistor inside the module to find the resistance values of the thermistor Rs corresponding to -20 °C and 85 °C, and obtain 68.2367 k ohm and 1.4521 k ohm.

[0086] According to the above queried resistance values, combined with the NTC detection circuit and the conversion formula, convert the voltage value of U in , and the conversion formula is:

[0087] U in = 3.3 * (R ntc / (R1 + R ntc ))

[0088] The calculated voltage U1 corresponding to high temperature is 0.4184 V, and the voltage U2 corresponding to low temperature is 2.8782 V; Figure 9 The figure shows the relationship diagram between temperature and voltage;

[0089] Finally, set the resistance values of R2, R3, R4, and R5 of the level comparison and conversion circuit so that the conditions 3.3 * R3 / (R2 + R3) = U1 and 3.3 * R4 / (R4 + R5) = U2 are satisfied.

[0090] The process of signal monitoring of the level conversion circuit is to monitor the high and low levels of the output level U o of the level comparison and conversion circuit. When U o is at a high level, execute the control instruction to output the corresponding PWM to drive the LED drive module to light up the LED light source module; when U o is at a low level, immediately turn off the PWM signal, thereby turning off the output of the LED light source module, as Figure 13 shown.

[0091] In addition, it should also be noted that if the output of the level comparison and conversion circuit is a high - level voltage control signal, the power supply of the drive signal processing module is kept connected through the power - on / off circuit of the drive signal processing module; if the output of the level comparison and conversion circuit is a low - level voltage control signal, the power supply of the drive signal processing module is disconnected through the power - on / off circuit of the drive signal processing module.

[0092] In this embodiment, the purpose of the power - on / off circuit of the drive signal processing module is to cut off the power supply of the signal processing module when the temperature is abnormal, that is, when the Uo output is at a low level, so as to turn off the PWM and thus turn off the output of the LED light source module;

[0093] When U o is at a high level, the NMOS transistor Q1 is turned on, and the PMOS transistor Q2 is also turned on. The power supply VDD1 flows through Q2 to VDD2 to supply power to the drive signal processing module. The drive signal processing module normally receives the PWM signal from the control unit, controls the LED drive module, and thus drives the LED light source module to emit light; when Uo is at a low level, the NMOS transistor Q1 cannot be turned on, and the PMOS transistor Q2 is also not turned on. The power supply VDD1 cannot flow through Q2 to VDD2, and the drive signal processing module cannot receive the PWM signal. The PWM signal is always low, and at this time, the lamp is forced to go out.

[0094] Or;

[0095] If the output of the level comparison and conversion circuit is a high-level voltage control signal, it performs an AND operation with the PWM control signal through the AND gate circuit module, and the operation result controls the normal operation of the light source module; if the output of the level comparison and conversion circuit is a low-level voltage control signal, it performs an AND operation with the PWM control signal through the AND gate circuit module, and the operation result controls the light source module to stop working.

[0096] In this embodiment, the function of the AND gate module is to perform an AND operation with PWM when the U o output is low, and the output is low, that is, when the system temperature is abnormal, there is no PWM output, so as to turn off the output of the LED light source module; when the U o output is high, that is, the system temperature is within the normal range, U o is 1, perform an AND operation with PWM, and the result is to follow PWM, and the LED lamp light source outputs normally and lights up, as shown in Table 1.

[0097] Table 1 U o Truth table of AND operation with PWM

[0098] Uo(Input1) PWM(Input2) Output 0 0 0 0 1 0 1 0 0 1 1 1

[0099] In addition, it should be noted that this embodiment of the present invention lists two implementation circuits of the AND gate module, but the implementation methods are not limited to these two: as Figure 11 shown is a kind of built with independent devices; as Figure 12 shown is a kind of using an AND gate chip, such as 74LS08D, etc.

[0100] To sum up, when the temperature inside the lamp body is within the normal range, the lamp completes the light output task normally according to the external control instruction; when the temperature inside the lamp body exceeds the normal range, the protection device immediately takes measures to cut off the internal PWM signal and forcibly turn off the light source output. After a period of time, when the temperature returns to the normal range, the PWM signal output is restored. There are two cases: when the low temperature is abnormal, since the environment cannot heat up, the performance is that the lamp is normally closed and cannot emit light until the environment warms up; when the high temperature is abnormal, the lamp generates protection and goes out, the temperature will stop rising, and after a period of time, when the temperature drops to the normal range, the lamp lights up again and repeats. When the above phenomena occur, the maintenance personnel can quickly check for abnormal defective chips and need to disassemble and repair them.

[0101] It can be understood that the content in the above method embodiments is applicable to this system embodiment. The functions specifically implemented by this system embodiment are the same as those in the above method embodiments, and the beneficial effects achieved are also the same as those in the above method embodiments.

[0102] The preferred embodiments of the embodiments of the present application have been described above with reference to the accompanying drawings, which do not limit the scope of rights of the embodiments of the present application. Any modifications, equivalent replacements, and improvements made by those skilled in the art without departing from the scope and essence of the embodiments of the present application shall fall within the scope of rights of the embodiments of the present application.

Claims

1. A lamp temperature detection circuit based on level comparison conversion, characterized in that: The circuit includes a control unit, a drive signal processing module, a power module, an LED drive module, a light source module and a level comparison conversion circuit. The light source module includes an NTC thermistor unit. The first output end of the power module is connected to the first input end of the control unit, the second output end of the power module is connected to the first input end of the drive signal processing module, the output end of the control unit is connected to the second input end of the drive signal processing module, the output end of the drive signal processing module is connected to the input end of the LED drive module, the output end of the LED drive module is connected to the input end of the light source module, the first output end of the light source module is connected to the second input end of the control unit, the second output end of the light source module is connected to the input end of the level comparison conversion circuit, and the output end of the level comparison conversion circuit is connected to the third input end of the control unit, wherein: The power supply module is used to provide a power supply signal to the control unit and the drive signal processing module; The control unit is used to output a PWM control signal according to the control instruction; The drive signal processing module is used to perform level matching and drive processing on the PWM control signal, and output a pre-processed PWM control signal; The LED driving module is used to obtain the pre-processed PWM control signal to perform constant current driving and constant voltage driving, and output PWM current; The light source module is used to receive the PWM current to emit light, and output a feedback temperature level signal through the NTC thermistor unit; The level comparison conversion circuit is used to perform temperature judgment according to the feedback temperature level signal, and control the operation of the control unit according to the temperature judgment result.

2. The circuit according to claim 1, characterized in that The NTC thermistor unit includes a first resistor and an NTC unit, a first end of the first resistor is connected to a high level signal, a second end of the first resistor is connected to a first pin of the NTC unit and obtains the feedback temperature level signal, and a second pin of the NTC unit is grounded.

3. The circuit according to claim 1, characterized in that The level comparison conversion circuit includes a first operational amplifier, a second operational amplifier, a second resistor, a third resistor, a fourth resistor, a fifth resistor and a thermistor, wherein the first end of the second resistor is connected to a high-level signal, the first end of the third resistor is grounded, the second end of the second resistor and the second end of the third resistor are connected to the negative phase input end of the first operational amplifier, the positive phase input end of the first operational amplifier is connected to the negative phase input end of the second operational amplifier and obtains the feedback temperature level signal, the first end of the fourth resistor is grounded, the first end of the fifth resistor is connected to a high-level signal, the second end of the fourth resistor and the second end of the fifth resistor are connected to the positive phase input end of the first operational amplifier, the control end of the first operational amplifier is connected to the first end of the thermistor and connected to the high-level signal, the control end of the second operational amplifier is grounded, and the output end of the first operational amplifier and the output end of the second operational amplifier are connected to the second end of the thermistor.

4. The circuit according to claim 1, characterized in that It also includes a drive signal processing module power supply disconnection circuit, the input end of the drive signal processing module power supply disconnection circuit is connected to the output end of the level comparison conversion circuit, the output end of the drive signal processing module power supply disconnection circuit is connected to the input end of the drive signal processing module, and the drive signal processing module power supply disconnection circuit is used to control the power off and on of the drive signal processing module according to the temperature judgment result.

5. The circuit according to claim 4, characterized in that The drive signal processing module power supply disconnection circuit includes a first MOS tube, a second MOS tube, a first diode, a sixth resistor and a seventh resistor, wherein the source of the second MOS tube is connected to the first end of the seventh resistor and connected to the first high level signal, the drain of the second MOS tube is connected to the second high level signal, the gate of the second MOS tube and the second end of the seventh resistor are connected to the drain of the first MOS tube, the positive terminal of the first diode is connected to the output end of the level comparison conversion circuit, the negative terminal of the first diode and the gate of the first MOS tube are connected to the first end of the sixth resistor, and the second end of the sixth resistor and the source of the first MOS tube are both grounded.

6. The circuit according to claim 1, characterized in that It also includes an AND gate circuit module, a first input end of the AND gate circuit module is connected to the output end of the level comparison conversion circuit, a second input end of the AND gate circuit module is connected to the output end of the control unit, and the output end of the AND gate circuit module is connected to the input end of the drive signal processing module, wherein the AND gate circuit module is used to control the operation of the light source module by performing an AND operation based on the temperature judgment result and the PWM control signal.

7. The circuit according to claim 6, characterized in that The AND gate circuit module includes an eighth resistor, a ninth resistor, a tenth resistor, a third MOS tube and a fourth MOS tube, wherein the first end of the eighth resistor and the first end of the tenth resistor are both connected to a high level signal, the first end of the ninth resistor is connected to the PWM control signal, the gate of the fourth MOS tube is connected to the temperature judgment result, the second end of the eighth resistor and the second end of the ninth resistor are connected to the drain of the third MOS tube and output a control signal, the second end of the tenth resistor and the gate of the third MOS tube are connected to the drain of the fourth MOS tube, and the source of the third MOS tube and the source of the fourth MOS tube are both grounded.

8. A detection method for a lamp temperature detection circuit based on level comparison conversion, characterized in that: The method comprises the following steps: Obtain PWM control signal and perform level matching and drive processing, and output pre-processed PWM control signal; The pre-processed PWM control signal is driven by constant current and constant voltage to output a current in PWM form; Controlling the operation of the light source module according to the PWM current, and outputting a feedback temperature level signal of the operation of the light source module through an NTC thermistor unit; The temperature is judged according to the feedback temperature level signal, and the operation of the control unit is controlled according to the temperature judgment result.

9. The method according to claim 8, characterized in that The step of performing temperature judgment according to the feedback temperature level signal and controlling the operation of the control unit according to the temperature judgment result includes: Determining a first threshold voltage and a second threshold voltage according to a resistance value of a level comparison conversion circuit; Determine the minimum operating temperature and the maximum operating temperature according to the allowable operating temperature range of the light source module; Determining a corresponding thermistor value according to the minimum operating temperature and the maximum operating temperature; Combining the NTC thermistor unit with the thermistor value to perform voltage conversion calculation to obtain a voltage value of the feedback temperature level signal; If the voltage value of the feedback temperature level signal is between the first threshold voltage and the second threshold voltage, a high level voltage control signal is output, otherwise, a low level voltage control signal is output; The high-level voltage control signal controls the control unit to continue to output the PWM control signal, and the low-level voltage control signal controls the control unit to stop outputting the PWM control signal, thereby controlling the operation of the control unit.

10. The method according to claim 9, characterized in that Also includes: If the output of the level comparison conversion circuit is the high-level voltage control signal, the power supply of the driving signal processing module is kept connected through the driving signal processing module power supply disconnection circuit; If the output of the level comparison conversion circuit is the low-level voltage control signal, the power supply of the driving signal processing module is disconnected by the driving signal processing module power supply disconnection circuit; or; If the output of the level comparison conversion circuit is the high-level voltage control signal, an AND operation is performed with the PWM control signal through an AND gate circuit module, and the operation result controls the light source module to work normally; If the output of the level comparison conversion circuit is the low-level voltage control signal, an AND operation is performed with the PWM control signal through an AND gate circuit module, and the operation result controls the light source module to stop working.

Images