A projector NTC hysteresis comparison control circuit

Abstract

This utility model relates to an NTC hysteresis comparator control circuit for a projector. The projector's NTC hysteresis comparator control circuit includes: a voltage regulator module for providing an input comparison voltage to a hysteresis comparator circuit module; a temperature input circuit module for converting the lamp panel temperature into a voltage signal and providing it to the hysteresis comparator circuit module; a hysteresis comparator circuit module for calculating an upper and lower threshold based on the input comparison voltage, and comparing the voltage signal with the upper and lower thresholds to output a corresponding level signal to a backlight control circuit module; and a backlight control circuit module for controlling the lamp panel backlight to turn on or off based on the level signal. This utility model eliminates the need for an additional temperature control switch on the light source connection line, simplifying the installation process and improving production efficiency. Furthermore, the precise temperature control mechanism effectively prevents equipment damage due to overheating, extending the projector's lifespan.

Description

Technical Field

[0001] This utility model relates to the field of projector control technology, and in particular to a projector NTC hysteresis comparison control circuit. Background Technology

[0002] In projectors, temperature control is a key factor in ensuring stable operation and extending the lifespan of the equipment. This is especially true for the projector's light source, which generates significant heat during prolonged high-brightness operation. Failure to effectively control the temperature can not only affect projection quality but also damage internal components and even lead to safety hazards. Therefore, monitoring and protection mechanisms for the light source temperature are of paramount importance.

[0003] Traditionally, a common method for controlling the temperature of a projector's light source is to add a temperature control switch to the light source connection line. This design prevents damage caused by overheating by disconnecting the circuit when the light source temperature reaches a preset threshold. However, this approach has several significant drawbacks:

[0004] High cost and installation difficulties: The introduction of temperature control switches not only increases material costs, but also requires consideration of their fixing position on the light source connection line, which increases the complexity and difficulty of installation. Especially in the compact internal structure of projectors, finding suitable fixing points and ensuring the reliability of electrical connections becomes a major challenge.

[0005] Poor anti-interference capability: Existing circuit designs are often relatively simple, typically using a conventional single-threshold comparator circuit to detect temperature and trigger protection actions. However, such circuits are particularly vulnerable to interference or noise affecting the input signal. Especially near the threshold level, any tiny fluctuation can cause the output level to repeatedly jump between high and low levels, leading to frequent switching of the light source. This not only affects the user experience but may also cause additional damage to the light source itself.

[0006] Stability and reliability issues: Due to insufficient anti-interference capabilities, traditional solutions struggle to achieve ideal stability and reliability in temperature control. Near the high-temperature protection point, repeated flickering of the light source not only interferes with normal projection use but may also shorten the light source's lifespan due to frequent current surges.

[0007] To address the aforementioned issues, developing a more efficient, stable, and economical temperature control solution for projectors is of paramount importance. Utility Model Content

[0008] The purpose of this invention is to overcome the shortcomings of the prior art and provide a projector NTC hysteresis comparison control circuit.

[0009] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0010] A projector NTC hysteresis comparator control circuit includes: a voltage regulator circuit module, a temperature input circuit module, a hysteresis comparator circuit module, and a backlight control circuit module. The voltage regulator circuit module provides an input comparison voltage to the hysteresis comparator circuit module. The temperature input circuit module converts the lamp panel temperature into a voltage signal and provides it to the hysteresis comparator circuit module. The hysteresis comparator circuit module calculates an upper threshold and a lower threshold based on the input comparison voltage, and compares the voltage signal with the upper threshold and the lower threshold to output a corresponding level signal to the backlight control circuit module. The backlight control circuit module controls the lamp panel backlight to turn on or off according to the level signal.

[0011] In one specific embodiment, the voltage regulator circuit module includes a voltage reference chip U2, resistors R5, R6, and R11. One end of resistor R5 is connected to the input voltage, and the other end is connected to one end of resistor R6. The other end of resistor R6 is connected to one end of resistor R11 and pin R of the voltage reference chip U2. The other end of resistor R11 is connected to pin A of the voltage reference chip U2. Pin K of the voltage reference chip U2 is connected to the hysteresis comparator circuit module.

[0012] In one specific embodiment, the temperature input circuit module includes a thermistor CN3, a resistor R4, a resistor R13, a lamp board CN2, and a thermistor RT. The lamp board CN2 is connected to the thermistor CN3, and the thermistor RT is connected to the lamp board CN2. Pin 2 of the thermistor CN3 is connected to the resistor R4 and the resistor R13. The resistor R13 is also connected to the hysteresis comparator circuit module.

[0013] In one specific embodiment, the hysteresis comparator circuit module includes a comparator chip U1, resistors R1, R2, and R3. Pin 3 of the comparator chip U1 is connected to resistor R13. One end of resistor R1 is connected to pin K of the voltage reference chip U2, and the other end is connected to pin 1 of the comparator chip U1 and resistor R2. Pin 4 of the comparator chip U1 is connected to resistors R2 and R3 and the backlight control circuit module.

[0014] In one specific embodiment, the backlight control circuit module includes a resistor R10, a transistor Q1, a resistor R12, a diode D1, a thermistor CN4, and a lamp board CN1. One end of the resistor R10 is connected to pin 4 of the comparator chip U1, and the other end is connected to pin 1 of the transistor Q1. Pin 3 of the transistor Q1 is connected to the resistor R12 and the diode D1. The diode D1 is also connected to the thermistor CN4. The thermistor CN4 is connected to the lamp board CN1, and the lamp board CN1 is connected to a plurality of LED beads.

[0015] In one specific embodiment, pin 2 of the thermistor CN3 is also connected to an electrostatic discharge protector DH01.

[0016] In one specific embodiment, the voltage reference chip U2 is model TL431.

[0017] In one specific embodiment, the thermistor RT is model RTQN0603X103F3950FB.

[0018] In one specific embodiment, the thermistor CN3 is model number GH1.25-0125-02-LT.

[0019] In one specific embodiment, the comparator chip U1 is model RS331XF.

[0020] The advantages of this invention compared to existing technologies are as follows: By integrating a voltage regulator circuit module, a temperature input circuit module, a hysteresis comparator circuit module, and a backlight control circuit module, there is no need to add an additional temperature control switch on the light source connection line, thus avoiding the material cost of the temperature control switch and the additional cost incurred during installation due to finding a fixed position; at the same time, it simplifies the installation process, improves production efficiency, significantly reduces overall costs, and makes installation more convenient; in addition, the hysteresis comparator circuit module design allows this module to calculate the upper and lower thresholds based on the precise input comparison voltage provided by the voltage regulator circuit module. The temperature input circuit module can convert the lamp panel temperature into a voltage signal in real time and accurately provide it to the hysteresis comparator circuit module. The hysteresis comparator circuit module compares this voltage signal with the pre-calculated upper and lower thresholds. When the lamp panel temperature reaches or exceeds the upper threshold, it outputs a high-level signal to the backlight control circuit module to control the lamp panel backlight to turn off, thus achieving high-temperature protection. When the temperature drops below the lower threshold, it outputs a low-level signal to restore the lamp panel backlight. This precise temperature control mechanism effectively prevents equipment damage caused by overheating and extends the lifespan of the projector.

[0021] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of this utility model, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 A schematic block diagram of the NTC hysteresis comparison control circuit for a projector provided by this utility model;

[0024] Figure 2 Schematic diagram of the NTC hysteresis comparison control circuit for projectors provided by this utility model Figure 1 ;

[0025] Figure 3 Schematic diagram of the NTC hysteresis comparison control circuit for projectors provided by this utility model Figure 2 ;

[0026] Figure 4 The transmission characteristic curve of the inverted input comparator provided by this utility model. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this utility model clearer, the present utility model will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0028] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present utility model.

[0029] In the description of this utility model, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this utility model and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model.

[0030] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this utility model, "a plurality of" means two or more, unless otherwise explicitly specified.

[0031] In this utility model, unless otherwise explicitly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0032] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0033] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. The illustrative expressions of the above terms in this specification should not be construed as necessarily referring to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. In addition, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0034] Please see Figure 1 , Figure 1A schematic block diagram of a projector NTC hysteresis comparator control circuit provided in an embodiment of this utility model includes: a voltage regulator circuit module 10, a temperature input circuit module 20, a hysteresis comparator circuit module 30, and a backlight control circuit module 40. The voltage regulator circuit module 10 provides an input comparison voltage to the hysteresis comparator circuit module 30. The temperature input circuit module 20 converts the lamp panel temperature into a voltage signal and provides it to the hysteresis comparator circuit module 30. The hysteresis comparator circuit module 30 calculates an upper threshold and a lower threshold based on the input comparison voltage, and compares the voltage signal with the upper threshold and the lower threshold to output a corresponding level signal to the backlight control circuit module 40. The backlight control circuit module 40 controls the lamp panel backlight to turn on or off according to the level signal.

[0035] Specifically, by integrating the voltage regulator circuit module 10, temperature input circuit module 20, hysteresis comparator circuit module 30, and backlight control circuit module 40, there is no need to add an additional temperature control switch on the light source connection line, thus avoiding the material cost of the temperature control switch and the additional cost incurred during installation due to finding a fixed position. At the same time, the installation process is simplified, production efficiency is improved, and the overall cost is significantly reduced, making installation more convenient. Furthermore, the hysteresis comparator circuit module 30 is designed to calculate the upper and lower threshold values ​​based on the precise input comparison voltage provided by the voltage regulator circuit module 10, as well as the temperature... The input circuit module 20 can convert the lamp panel temperature into a voltage signal in real time and accurately provide it to the hysteresis comparator circuit module 30. The hysteresis comparator circuit module 30 compares the voltage signal with the pre-calculated upper and lower thresholds. When the lamp panel temperature reaches or exceeds the upper threshold, it outputs a high-level signal to the backlight control circuit module 40 to control the lamp panel backlight to turn off, thus achieving high-temperature protection. When the temperature drops below the lower threshold, it outputs a low-level signal to restore the lamp panel backlight. This precise temperature control mechanism effectively prevents equipment damage caused by overheating and extends the lifespan of the projector.

[0036] Please see Figure 1 and Figure 2 In one embodiment, the voltage regulator circuit module 10 includes a voltage reference chip U2, resistors R5, R6, and R11. One end of resistor R5 is connected to the input voltage, and the other end is connected to one end of resistor R6. The other end of resistor R6 is connected to one end of resistor R11 and pin R of the voltage reference chip U2. The other end of resistor R11 is connected to pin A of the voltage reference chip U2. Pin K of the voltage reference chip U2 is connected to the hysteresis comparator circuit module 30.

[0037] Specifically, the voltage reference chip U2, as the core component, has the following pin functions: Pin R (reference terminal): Receives the voltage signal after voltage division, used to adjust the output regulated voltage value. Pin A (anode): Grounded, forming a current loop. Pin K (cathode): Outputs a stable voltage, connected to the input terminal of the hysteresis comparator circuit module 30. One end of resistor R5 is connected to the input voltage (e.g., 3.3V), and the other end is connected to resistor R6. The other end of resistor R6 is connected to resistor R11 and pin R of the voltage reference chip U2. The other end of resistor R11 is connected to pin A (grounded) of the voltage reference chip U2.

[0038] The input voltage is divided by resistors R5, R6, and R11, forming a feedback voltage at pin R of the voltage reference chip U2. The internal comparator of voltage reference chip U2 compares the voltage at pin R with an internal reference voltage (e.g., 2.5V), adjusting the output current at pin K to stabilize the voltage at pin R at the reference value. Finally, a stable 2.5V voltage is formed at the connection point of resistors R5 and R6 (near pin R of voltage reference chip U2), serving as the input comparison voltage (VREF) for the hysteresis comparator.

[0039] Please see Figures 1 to 3 In one embodiment, the hysteresis comparator circuit module 30 includes a comparator chip U1, resistors R1, R2, and R3. Pin 3 of the comparator chip U1 is connected to resistor R13. One end of resistor R1 is connected to pin K of the voltage reference chip U2, and the other end is connected to pin 1 of the comparator chip U1 and resistor R2. Pin 4 of the comparator chip U1 is connected to resistor R2, resistor R3, and the backlight control circuit module 40.

[0040] Specifically, the pin functions of comparator chip U1 are as follows: Pin 1 (inverting input): Connects to the voltage divider node of resistors R1 and R2, receiving the input voltage signal (Vin). Pin 3 (input signal): Connects to the output of temperature input circuit module 20 (through resistor R13), receiving the voltage signal (Vin) converted from the lamp board temperature. Pin 4 (output): Connects to resistors R2 and R3 and backlight control circuit module 40, outputting high and low level signals (Vout). One end of resistor R1 is connected to the 2.5V input comparison voltage output from voltage regulator circuit module 10 (pin K of voltage reference chip U2), and the other end is connected to pin 1 of comparator chip U1 and resistor R2. One end of resistor R2 is connected to pin 1 of comparator chip U1, and the other end is connected to pin 4 of comparator chip U1 and resistor R3. One end of resistor R3 is connected to pin 4 of comparator chip U1, and the other end is connected to the input voltage.

[0041] More specifically, the calculation formula is as follows:

[0042] UH=VREF*(R2+R3) / (R1+R2+R3)+VCC*R1 / (R1+R2+R3);

[0043] UL = VREF * R2 / (R1 + R2);

[0044] Where VREF = 2.5V, VCC = 3.3V; UH is the upper threshold and UL is the lower threshold.

[0045] Substituting the values ​​into the equation:

[0046] UH=2.5*(180+1) / (10+180+1)+3.3*10 / (10+180+1)=2.54189V;

[0047] UL=2.5*180 / (10+180)=2.36842V.

[0048] Please see Figure 4 When the Vin voltage is lower than UH, Vout outputs a high level; when the Vin voltage is higher than UL, Vout outputs a low level; when the Vin voltage is between UL and UH, if the Vin voltage rises slowly from UL to UH, Vout outputs a high level; if the Vin voltage falls slowly from UH to UL, Vout outputs a low level.

[0049] Please see Figures 1 to 3 In one embodiment, the temperature input circuit module 20 includes a thermistor CN3, a resistor R4, a resistor R13, a lamp board CN2, and a thermistor RT. The lamp board CN2 is connected to the thermistor CN3, and the thermistor RT is connected to the lamp board CN2. Pin 2 of the thermistor CN3 is connected to the resistor R4 and the resistor R13. The resistor R13 is also connected to the hysteresis comparator circuit module 30.

[0050] Specifically, the temperature input circuit module 20 converts the lamp board temperature into a voltage signal (Vin) that can be recognized by the hysteresis comparator through a combination of a negative temperature coefficient thermistor (NTC) and a voltage divider resistor, as implemented below:

[0051] A thermistor RT (resistance 10kΩ at 25℃, decreasing with temperature) is mounted on lamp board CN2 to directly sense the lamp board temperature. Thermistor CN3 is a spare or redundant design; its pin 2 is connected to resistors R4 and R13. One end of resistor R4 is connected to the power supply VCC (3.3V), and the other end is connected to pin 2 of thermistor CN3 and resistor R13. One end of resistor R13 is connected to pin 2 of thermistor CN3, and the other end is connected to pin 3 of comparator chip U1. Lamp board CN2 is connected to thermistor RT via wires, forming a temperature sampling point and ensuring tight thermal coupling between RT and the lamp board. Thermistor CN3 is connected in parallel with thermistor RT; if thermistor RT fails unexpectedly, thermistor CN3 can replace it for temperature sampling, improving system reliability.

[0052] More specifically, UH = 2.54189V, calculated using the formula: UH = 3.3 * RT / (RT + 0.36k), yielding RT = 1.207K, and then the NTC temperature is approximately 81°C according to the table; UL = 2.36842V, calculated using the formula: UL = 3.3 * RT / (RT + 0.36k), yielding RT = 0.9152K, and then the NTC temperature is approximately 89°C according to the table.

[0053] Therefore, it can be seen that when the lamp board temperature slowly rises from room temperature, the Vin level slowly decreases, and the Vout output is low. When the lamp board temperature reaches 89°, that is, when the Vin voltage reaches UL = 2.36842V, the Vout output is high. Similarly, when the lamp board temperature slowly decreases from a high temperature of 89°, the Vout output is high. When the lamp board temperature is below 81°, that is, when the Vin voltage reaches UH = 2.54189V, the Vout output is low.

[0054] Please see Figures 1 to 3 In one embodiment, the backlight control circuit module 40 includes a resistor R10, a transistor Q1, a resistor R12, a diode D1, a thermistor CN4, and a lamp board CN1. One end of the resistor R10 is connected to pin 4 of the comparator chip U1, and the other end is connected to pin 1 of the transistor Q1. Pin 3 of the transistor Q1 is connected to the resistor R12 and the diode D1. The diode D1 is also connected to the thermistor CN4. The thermistor CN4 is connected to the lamp board CN1, and the lamp board CN1 is connected to a plurality of LED beads.

[0055] Specifically, the backlight control circuit module 40, through the switching action of transistor Q1 and the cooperation of peripheral components, controls the on / off state of the LED backlight based on the output signal (Vout) of the hysteresis comparator. The specific implementation is as follows:

[0056] One end of resistor R10 is connected to pin 4 (output) of comparator chip U1, and the other end is connected to the base (pin 1, taking an NPN transistor as an example), serving as a current limiting protection to prevent excessive comparator output current from damaging transistor Q1. The base (pin 1) of transistor Q1 receives the Vout signal (high / low level) through resistor R10, its collector (pin 3) is connected to resistor R12 and the anode of diode D1, and its emitter (pin 2) is grounded. One end of resistor R12 is connected to the collector of transistor Q1, and the other end is connected to the anode of diode D1, serving as a current limiting protection to prevent damage to the LED due to excessive current. The anode of diode D1 is connected to resistor R12, and its cathode is connected to the thermistor CN4, serving as reverse voltage protection to prevent damage to the LED due to reverse power connection. One end of the thermistor CN4 is connected to the cathode of D1, and the other end is connected to the lamp board CN1 to sample the temperature of the lamp board. The lamp board CN1 is connected to several LED beads (such as the 1Q42A model) as a backlight source, and its on / off state is controlled by the switching state of the transistor Q1.

[0057] When comparator chip U1 outputs a low level, there is no current at the base of transistor Q1, so transistor Q1 is cut off. The collector voltage is pulled high to the power supply voltage (VCC) by resistor R12, the cathode voltage of diode D1 is high, and the LED is powered on through the lamp board CN1, turning on the backlight. When comparator chip U1 outputs a high level, the base current of transistor Q1 conducts through resistor R10, transistor Q1 saturates, the collector voltage approaches 0V, the cathode voltage of diode D1 is low, the LED is powered off, and the backlight is off.

[0058] Please see Figure 2 In one embodiment, pin 2 of the thermistor CN3 is also connected to an electrostatic discharge protector DH01.

[0059] Specifically, pin 2 of the thermistor CN3 serves as a critical node for temperature signal input. Electrostatic discharge (ESD) protection is achieved through a series connection with an electrostatic discharge (ESD) protector DH01. The implementation is as follows: Pin 2 of the thermistor CN3 is the temperature sampling signal output terminal, connected to voltage divider resistors R4 and R13 (forming the Vin voltage input), and simultaneously connected in parallel with the ESD protector DH01. One end of the ESD protector DH01 is connected to pin 2 of the thermistor CN3, and the other end is grounded (GND). The signal from pin 2 of the thermistor CN3 is filtered by the ESD protector DH01 and then transmitted to the subsequent voltage divider circuit (resistors R4 and R13) and the hysteresis comparator (U1).

[0060] When the electrostatic discharge (ESD) protector DH01 is in a high-resistance state (>1MΩ), it has no effect on the temperature sampling signal (Vin), ensuring complete signal transmission. When pin 2 of the thermistor CN3 experiences electrostatic discharge (such as human contact or environmental interference), the ESD protector DH01 quickly conducts (response time <1ns), discharging the electrostatic current to ground and preventing high voltage damage to subsequent circuits (such as the hysteresis comparator U1, resistor R4, and resistor R13). After the electrostatic discharge disappears, the ESD protector DH01 automatically returns to the high-resistance state, and the circuit resumes normal operation.

[0061] In one embodiment, the voltage reference chip U2 is model TL431.

[0062] Specifically, the TL431, as a voltage reference chip, provides a high-precision, low-drift 2.5V reference voltage (VREF) for the hysteresis comparator, significantly improving the stability, reliability, and cost-effectiveness of the temperature control system.

[0063] In one embodiment, the thermistor RT is of model RTQN0603X103F3950FB.

[0064] Specifically, the thermistor RT selected is RTQN0603X103F3950FB (negative temperature coefficient NTC thermistor), whose core parameter (resistance of 10kΩ at 25℃) provides a high-precision, high-reliability and high-integration solution for temperature sampling, significantly improving the projector's high-temperature protection and low-temperature recovery performance.

[0065] In one embodiment, the thermistor CN3 is model number GH1.25-0125-02-LT.

[0066] Specifically, the thermistor CN3 is selected as GH1.25-0125-02-LT, which provides high reliability, high integration and anti-interference capability for temperature sampling, and significantly improves the temperature control performance of the projector in complex environments.

[0067] In one embodiment, the comparator chip U1 is model RS331XF.

[0068] Specifically, the comparator chip U1 uses RS331XF, which provides a highly reliable, highly anti-interference, and low-power solution for the hysteresis comparison function, significantly improving the performance of the projector's temperature control system.

[0069] In this utility model, the various components, their models, and connection relationships that are not explicitly stated are... Figures 2 to 3 The specific circuit diagram is already shown, so it will not be described again here.

[0070] The above embodiments are preferred implementations of this utility model. In addition, this utility model can also be implemented in other ways. Any obvious substitutions without departing from the concept of this technical solution are within the protection scope of this utility model.

Claims

1. A projector NTC hysteresis comparison control circuit, characterized in that, include: The system includes a voltage regulator circuit module, a temperature input circuit module, a hysteresis comparator circuit module, and a backlight control circuit module. The voltage regulator circuit module provides an input comparison voltage to the hysteresis comparator circuit module. The temperature input circuit module converts the lamp panel temperature into a voltage signal and provides it to the hysteresis comparator circuit module. The hysteresis comparator circuit module calculates an upper threshold and a lower threshold based on the input comparison voltage, and compares the voltage signal with the upper threshold and lower threshold to output a corresponding level signal to the backlight control circuit module. The backlight control circuit module controls the lamp panel backlight to turn on or off based on the level signal.

2. The projector NTC hysteresis comparison control circuit according to claim 1, characterized in that, The voltage regulator circuit module includes a voltage reference chip U2, resistors R5, R6, and R11. One end of resistor R5 is connected to the input voltage, and the other end is connected to one end of resistor R6. The other end of resistor R6 is connected to one end of resistor R11 and pin R of the voltage reference chip U2. The other end of resistor R11 is connected to pin A of the voltage reference chip U2. Pin K of the voltage reference chip U2 is connected to the hysteresis comparator circuit module.

3. The projector NTC hysteresis comparison control circuit according to claim 2, characterized in that, The temperature input circuit module includes a thermistor CN3, a resistor R4, a resistor R13, a lamp board CN2, and a thermistor RT. The lamp board CN2 is connected to the thermistor CN3, and the thermistor RT is connected to the lamp board CN2. Pin 2 of the thermistor CN3 is connected to the resistor R4 and the resistor R13. The resistor R13 is also connected to the hysteresis comparator circuit module.

4. The projector NTC hysteresis comparison control circuit according to claim 3, characterized in that, The hysteresis comparator circuit module includes a comparator chip U1, resistors R1, R2, and R3. Pin 3 of the comparator chip U1 is connected to resistor R13. One end of resistor R1 is connected to pin K of the voltage reference chip U2, and the other end is connected to pin 1 of the comparator chip U1 and resistor R2. Pin 4 of the comparator chip U1 is connected to resistors R2, R3, and the backlight control circuit module.

5. The projector NTC hysteresis comparison control circuit according to claim 4, characterized in that, The backlight control circuit module includes a resistor R10, a transistor Q1, a resistor R12, a diode D1, a thermistor CN4, and a lamp board CN1. One end of the resistor R10 is connected to pin 4 of the comparator chip U1, and the other end is connected to pin 1 of the transistor Q1. Pin 3 of the transistor Q1 is connected to the resistor R12 and the diode D1. The diode D1 is also connected to the thermistor CN4. The thermistor CN4 is connected to the lamp board CN1, and the lamp board CN1 is connected to several LED beads.

6. The projector NTC hysteresis comparison control circuit according to claim 3, characterized in that, The thermistor CN3 is also connected to an electrostatic discharge protector DH01 at pin 2.

7. The projector NTC hysteresis comparison control circuit according to claim 3, characterized in that, The voltage reference chip U2 is model TL431.

8. The projector NTC hysteresis comparison control circuit according to claim 3, characterized in that, The thermistor RT is model RTQN0603X103F3950FB.

9. The projector NTC hysteresis comparison control circuit according to claim 3, characterized in that, The thermistor CN3 is model number GH1.25-0125-02-LT.

10. The projector NTC hysteresis comparison control circuit according to claim 4, characterized in that, The comparator chip U1 is model RS331XF.

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