Automatic heating and defrosting system for camera

Abstract

The present invention discloses an automatic heating and defrosting system for a camera, comprising an NTC resistor and a MOS tube, wherein the NTC resistor is connected to the G pole (gate) of the MOS tube, and is used to adjust the conduction state of the MOS tube by monitoring temperature changes; the output end is the S pole (source) of Q1 (MOS tube), and the input ends VCC and GND provide power and ground wire for the circuit respectively; a PTC thermistor is connected to the output end of the MOS tube; wherein the G pole of the MOS tube is provided with a first resistor, a second resistor (NTC resistor), and the source is provided with a third resistor (RTC resistor), the first resistor is connected to the input end VCC, indicating a high level; the second resistor (NTC resistor) is connected to the G pole of the MOS tube; the third resistor (RTC resistor) is connected to the source of the MOS tube. The present invention does not directly read the NTC resistor voltage division value, but controls the on and off of the MOS tube by different voltage division values ​​of the NTC resistor at different temperatures to achieve heating control. It can be widely used in various camera devices that require heating and defrosting.

Description

Technical Field

[0001] The present invention relates to the technical field of cameras, and in particular to an automatic heating and defrosting system for cameras. Background Art

[0002] The camera automatic heating and defrosting system is used to automatically monitor and control the heating and defrosting process of the camera. The system is mainly used in various outdoor camera equipment, especially in cold and humid environments, to maintain the clarity of the camera lens and prevent condensation and frost from affecting the shooting effect.

[0003] Most of the existing methods for automatic heating and defrosting of cameras use the NTC resistor built into the heating lens. The resistance value is different at different temperatures. By collecting and calculating the NTC resistance value, the corresponding ambient temperature is obtained, thereby starting the drive circuit and energizing the lens heating wire (PTC resistor) to achieve the purpose of defrosting. Although the NTC resistor can roughly reflect the change in temperature, the relationship between its resistance and temperature is nonlinear, so the calculated temperature value has a certain error. Since the resistance change of the NTC resistor takes time, this method may lag behind the actual temperature change in an environment with rapid temperature changes. If the heating circuit is always in operation, it will consume a certain amount of electrical energy, especially in a continuous low temperature environment, the energy consumption will increase further. If the heating wire cannot evenly heat the lens surface, some parts of the lens may become blurred or condensation may occur. In extreme environmental conditions, such as extremely cold or extremely hot climates, existing systems may not work effectively.

[0004] Therefore, this application considers how to improve the accuracy and response speed of temperature detection, and how to optimize the design and layout of heating elements to develop a more intelligent and adaptive camera automatic heating and defrosting system. Summary of the invention

[0005] In view of the above problems, the present invention is proposed to provide a camera automatic heating and defrosting system that overcomes all or at least part of the above problems.

[0006] According to one aspect of the present invention, a camera automatic heating and defrosting system is provided, comprising:

[0007] NTC resistor and MOS tube, the NTC resistor is connected to the gate of the MOS tube, and is used to adjust the conduction state of the MOS tube by monitoring temperature changes;

[0008] Input terminals VCC and GND provide power and ground for the circuit respectively;

[0009] A PTC heating resistor, which is a lens heating wire component, is connected to the S source of the MOS;

[0010] Among them, the input end of the MOS is provided with a first resistor, a second resistor, and a third resistor. The first resistor is connected to the input end VCC, indicating a high level; the second resistor NTC resistor is connected to the input end VCC, and the third resistor PTC resistor is connected to the output end S source.

[0011] Furthermore, the first resistor is a calibration resistor used to set a starting heating temperature of the heating lens.

[0012] Furthermore, a feedback circuit is provided inside the voltage regulator circuit;

[0013] When the input voltage increases or decreases, the feedback circuit adjusts the parameters of the internal components accordingly to keep the output voltage stable.

[0014] Furthermore, the PTC resistor is used to heat the lens when the ambient temperature is lower than the lens surface temperature, so that the lens surface temperature is higher than the ambient temperature to avoid water vapor condensation on the lens surface; and, when the lens surface temperature reaches a preset threshold, heating is stopped to prevent the lens from overheating for a long time.

[0015] Furthermore, the MOS tube controls the heating and stopping of the heating of the PTC resistor;

[0016] Among them, when the gate-source voltage Vgs of the MOS tube is greater than the turn-on voltage threshold Vgsth value, the MOS tube is turned on and the PTC resistor starts to heat; when the gate-source voltage Vgs of the MOS tube is less than the Vgsth value, the MOS tube is disconnected and the PTC resistor stops heating.

[0017] Furthermore, the feedback circuit includes a voltage detector and an error amplifier;

[0018] The voltage detector is used to detect the change of the output voltage and transmit the detected voltage change signal to the error amplifier;

[0019] The error amplifier adjusts the parameters of the internal components according to the voltage variation signal to control the stability of the output voltage.

[0020] Furthermore, the first resistor and the second resistor have the same resistance value to balance the input signal of the NAND gate.

[0021] Furthermore, the resistance value of the third resistor is adjusted by a control instruction sent by a control system to the NAND gate circuit.

[0022] Furthermore, the control system automatically generates a control instruction based on the monitored performance parameters of the NAND gate circuit and sends the control instruction to the NAND gate circuit.

[0023] Furthermore, the control instructions include adjustment instructions and target resistance control instructions;

[0024] The calculation formula of the target resistance is:

[0025]

[0026] Among them, R target is the target resistance, R Initial is the initial resistance, ΔT is the temperature change, TCR is the temperature coefficient of resistance, ΔH is the humidity change, HCR is the humidity coefficient of resistance, K1 and K2 are correction coefficients.

[0027] According to the scheme provided by the present invention, it includes an NTC resistor and a MOS tube, wherein the NTC resistor is connected to the gate of the MOS tube and is used to adjust the conduction state of the MOS tube by monitoring temperature changes; a voltage regulator circuit, whose input end is VCC and the output end is 12V, and the input ends VCC and GND provide power and ground for the circuit respectively; a PTC thermistor, connected to the S source of the MOS; wherein the input end of the MOS is provided with a first resistor (calibration resistor) and a second resistor (NTC resistor), the first resistor is connected to the voltage regulator, indicating a high level; the second resistor is connected to the G gate, and the third resistor is connected to the S source.

[0028] The present invention does not directly read the NTC resistor voltage division value, but controls the on and off of the MOS tube through the different voltage division values ​​of the NTC resistor at different temperatures to achieve heating control. It can be widely used in various camera devices that require heating and defrosting.

[0029] Beneficial Effects

[0030] (1) By combining NTC resistors, MOS tubes, voltage regulator circuits and other components, accurate temperature monitoring and regulation, stable power management, adaptive temperature control, and efficient heating and stopping control are achieved. When the ambient temperature is lower than the lens surface temperature, the NTC resistor will automatically heat the lens to make the lens surface temperature higher than the ambient temperature to avoid condensation. At the same time, when the lens surface temperature reaches the preset threshold, the system will automatically stop heating to prevent the lens from overheating for a long time.

[0031] (2) By providing adjustment instructions and target resistance control instructions, and using an accurate target resistance calculation formula, more flexible and accurate temperature and humidity control is achieved, which improves the stability and reliability of the camera and meets the needs of different applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present invention. Moreover, the same reference symbols are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0033] Figure 1 A circuit diagram of an automatic heating and defrosting system for a camera according to an embodiment of the present invention is shown;

[0034] Figure 2 A circuit diagram of an existing camera automatic heating and defrosting method is shown. DETAILED DESCRIPTION

[0035] The exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided in order to enable a more thorough understanding of the present invention and to enable the scope of the present invention to be fully communicated to those skilled in the art.

[0036] Figure 1 The circuit diagram of the automatic heating and defrosting system for a camera according to an embodiment of the present invention is shown. The automatic heating and defrosting system for a camera according to an embodiment of the present invention comprises:

[0037] NTC resistor and MOS tube, the NTC resistor is connected to the gate of the MOS tube, and is used to adjust the conduction state of the MOS tube by monitoring temperature changes;

[0038] The MOS tube has VCC and GND as input terminals and S (source) as output terminals. The input terminals VCC and GND provide power and ground for the circuit respectively.

[0039] PTC thermistor, which is the lens heating wire component, is connected to the S (source) of the MOS tube;

[0040] The input end of the MOS circuit is provided with a first resistor (R1), a second resistor (NTC), and a third resistor (PTC); the first resistor (R1) is connected to the voltage regulator at the input end, indicating a high level; the second resistor is connected to the gate of the MOS tube, and the third resistor is connected to the source of the MOS tube.

[0041] The principle of frost on the outer surface of the lens is: when air containing water vapor (temperature is T1) comes into contact with a cold lens (surface temperature is T2), when T1>T2, it will liquefy into water mist and droplets on the lens surface. When the temperature of T2 is less than 0 degrees, frost will form.

[0042] In this embodiment, defrosting is performed by suppressing lens fogging. The basic mechanism of defrosting is to increase the temperature of T2 and maintain the temperature greater than T1, T2>0°C, so that moisture in the air cannot condense on the lens surface, thereby achieving the effect of suppressing lens fogging and defrosting.

[0043] like Figure 2 As shown, the existing camera automatic heating and defrosting method includes power supply, sensor, controller and other parts. Among them, the power supply of the camera is 1.8V, and the communication interface of the camera uses MII / CSI (4 channels) and frame synchronization signals. The image sensor uses the "heat coil" component. The controller interacts with the sensor through the "mclk" and "sensor reset" signals. The back-end controller reads the voltage divider value of the NTC resistor through the Serializer to obtain the temperature of the lens, and controls the on and off of the MOS tube by sending commands to the Serializer to achieve heating control.

[0044] In this embodiment, the NTC resistance value is not read directly. Figure 1 As shown, the built-in NTC resistor of the heating lens has different resistance values ​​at different temperatures. Through the feedback circuit, when the temperature is lower than the set threshold, the drive circuit is automatically started to energize the lens heating wire to achieve the purpose of defrosting. The hardware design is simple, reducing costs, and does not require the module's ADC sampling resources, back-end participation, and complex logic design.

[0045] The workflow of this embodiment is as follows:

[0046] VCC and GND serve as inputs to provide power and ground for the entire circuit respectively.

[0047] At the input of the MOS, the R1 resistor is connected to the voltage regulator, indicating a high level. At the same time, the NTC thermistor is connected to the gate of the MOS tube. When the temperature rises, the resistance of the NTC will decrease.

[0048] The voltage regulator stabilizes VCC at the input and provides it to R1. The function of the voltage regulator is to keep the output voltage stable so that the calibration circuit can operate normally. The reasons why the voltage regulator can keep the output voltage stable are as follows:

[0049] The voltage regulator has a feedback circuit inside that can detect changes in the output voltage. When the output voltage increases or decreases, the feedback circuit will adjust the parameters of the internal components accordingly to keep the output voltage stable. In addition, the voltage regulator usually has a large input and output voltage range, so it can keep the output voltage stable within a wide power supply voltage range. The voltage regulator plays the role of regulating and stabilizing the output voltage in the circuit, thereby ensuring the normal operation of the circuit.

[0050] Furthermore, the resistance of the first resistor (calibration resistor) is 100K (reference value). The resistor is used to calibrate and adjust the automatic heating environment temperature threshold and range of the temperature control circuit.

[0051] Furthermore, a feedback circuit is provided inside the voltage regulator circuit;

[0052] When the output voltage increases or decreases, the feedback circuit adjusts the parameters of the internal components accordingly to keep the output voltage stable, so that the calibration circuit always works at the designed value and does not cause changes in the heating temperature start threshold due to fluctuations in the VCC voltage.

[0053] Furthermore, the PTC resistor is used to heat the lens when the ambient temperature is lower than the lens surface temperature, so that the lens surface temperature is higher than the ambient temperature to avoid water vapor condensation on the lens surface; and, when the lens surface temperature reaches a preset threshold, heating is stopped to prevent the lens from overheating for a long time.

[0054] Furthermore, the MOS tube controls the heating and stopping of the heating of the PTC resistor;

[0055] Among them, when the gate-source voltage Vgs of the MOS tube is greater than the turn-on voltage threshold Vgsth value, the MOS tube is turned on and the PTC resistor starts to heat; when the gate-source voltage Vgs of the MOS tube is less than the Vgsth value, the MOS tube is disconnected and the PTC resistor stops heating.

[0056] In this embodiment, the ambient temperature is 0 degrees. At this time, the NTC resistor is 27.28K, and the VGS voltage is 2.57V. It is greater than the Vgsth of the MOS tube. At this time, the Q1-NMOS tube is in the on state, and the PTC resistor inside the lens is in the heating power-on state, so that the lens is heated and the lens surface is ensured to be much higher than the ambient temperature, so as to prevent water vapor in the air from condensing on the lens surface.

[0057] When the lens surface temperature continues to rise, the NTC resistance value continues to decrease. When the lens surface temperature reaches 30 degrees, the NTC resistance value is 8.312K. At this time, the VGS voltage is 0.92V, which is less than the Vgsth of the MOS tube. At this time, Q1-NMOS is disconnected, and the PTC resistor inside the lens is powered off, and the heating stops. Avoid long-term lens heating.

[0058] After stopping heating, the lens cools down slowly. When the temperature drops to a certain threshold, the Vgs voltage is greater than Vgsth, and the lens resumes heating and temperature rises, so that the lens surface temperature is always greater than the ambient temperature, and frost cannot form.

[0059] Furthermore, the feedback circuit further includes a voltage detector and an error amplifier (not shown in the figure);

[0060] The voltage detector is used to detect the change of the output voltage and transmit the detected voltage change signal to the error amplifier;

[0061] The error amplifier adjusts the parameters of the internal components according to the voltage variation signal to control the stability of the output voltage.

[0062] The working principle is as follows: the voltage detector constantly monitors the output voltage, and when the output voltage changes, the voltage detector converts it into an electrical signal. The electrical signal is passed to the error amplifier, which compares the electrical signal with the expected voltage and generates an error signal, which represents the difference between the actual output voltage and the expected output voltage. The error amplifier receives the voltage change signal from the voltage detector, and its task is to adjust the output voltage according to these change signals to keep it stable.

[0063] In this embodiment, by monitoring the change of the output voltage in real time and adjusting the parameters of the internal components to control the stability of the output voltage, the stability and reliability of the system are improved. The voltage detector can be a voltmeter or a voltage sensor, which is used to detect the change of the output voltage in real time. When the output voltage changes, the voltage detector transmits the detected voltage change signal to the error amplifier. After receiving the voltage change signal, the error amplifier adjusts the parameters of the internal components according to the set control algorithm, such as adjusting the parameters of the variable resistor or capacitor in the voltage regulator circuit to control the stability of the output voltage. For example, the system sets the output voltage to 5V. When the load suddenly increases and causes the output voltage to drop, the voltage detector will detect the change signal of the voltage drop and pass the signal to the error amplifier. The error amplifier adjusts the parameters of the internal components according to the set control algorithm, such as increasing the resistance of the variable resistor or reducing the capacity of the variable capacitor, etc., to reduce the output current and stabilize the output voltage. Through this real-time feedback and adjustment mechanism, the system can quickly respond to changes in the output voltage and keep the output voltage stable.

[0064] Furthermore, the first resistor and the second resistor have the same resistance value to balance the input signal of the NAND gate.

[0065] The NAND gate has two input terminals and one output terminal. When two input signals arrive at the NAND gate at the same time, they are divided by the first resistor and the second resistor. If the resistance values ​​of the first resistor and the second resistor are different, the two input signals may have different voltage levels before reaching the NAND gate, resulting in circuit instability. In order to make the two input signals of the NAND gate have the same voltage level, the two input signals are connected to the input terminals of the NAND gate through two resistors of equal resistance. No matter how the source voltage of the input signal changes, the voltage received by the two input terminals is equal, thus ensuring the balance of the input signal.

[0066] Therefore, by making the first resistor and the second resistor have the same resistance value, the input signal of the NAND gate can be balanced, thereby reducing errors and improving system stability.

[0067] Furthermore, the resistance value of the third resistor is adjusted by a control instruction sent by a control system to the NAND gate circuit.

[0068] The control system (not shown in the figure, including a microprocessor, storage and communication interface, etc.) sends a control instruction to the third resistor to change its resistance value. For example, if the control system detects that a parameter such as output voltage, current or temperature in the circuit deviates from an expected range, a control instruction is sent to the third resistor to adjust its resistance value to change the circuit behavior, thereby restoring the performance parameter to the expected range.

[0069] Specifically, two resistors with the same resistance are selected as the first resistor and the second resistor, and connected to the input end of the NAND gate. The two input signals received by the NAND gate will have the same amplitude, which can improve the logic judgment accuracy of the NAND gate and reduce the error caused by the imbalance of the input signal.

[0070] Furthermore, the control system automatically generates a control instruction based on the monitored performance parameters of the NAND gate circuit and sends the control instruction to the NAND gate circuit.

[0071] The control system (not shown in the figure) obtains the working status of the NAND gate circuit in real time by monitoring the performance parameters of the NAND gate circuit, such as the level and logic state of the input signal. The logic judgment unit inside the control system automatically generates corresponding control instructions, such as adjusting the amplitude of the input signal, changing the logic state, etc., to optimize the working effect of the NAND gate circuit. Then, the control system sends the generated control instructions to the NAND gate circuit to achieve precise control of the NAND gate circuit.

[0072] Furthermore, the control instructions include adjustment instructions and target resistance control instructions;

[0073] The calculation formula of the target resistance is:

[0074]

[0075] Among them, R target is the target resistance, R Initial is the initial resistance, ΔT is the temperature change, TCR is the temperature coefficient of resistance, ΔH is the humidity change, HCR is the humidity coefficient of resistance, K1 and K2 are correction coefficients.

[0076] By introducing the target resistance control instruction and the precise target resistance calculation formula, the control system can more intelligently adjust parameters such as temperature and humidity. During the heating and defrosting process, if the temperature and humidity cannot be controlled in a timely and accurate manner, the heating element will overheat, thereby damaging the lens or heating element. The introduction of temperature and humidity monitoring can timely detect and adjust the heating power of the heating element to avoid the occurrence of overheating problems. Specifically, the control system automatically calculates the target resistance based on the monitored environmental parameters (such as temperature and humidity) and the performance parameters of the NAND gate circuit. Then, according to the target resistance and the generation logic of the control instruction, the control system generates an adjustment instruction and a target resistance control instruction. The adjustment instruction is used to adjust the input signal amplitude, logic state and other parameters of the NAND gate circuit to achieve the control target. The standard resistance control instruction is used to control the heating power and other parameters of the heating element to achieve precise temperature control. For example, when the system detects that the ambient temperature is lower than the set threshold, the control system automatically calculates the target resistance and generates an adjustment instruction and a target resistance control instruction according to the target resistance and the generation logic of the control instruction. The adjustment instruction will instruct the NAND gate circuit to adjust the amplitude or logic state of the input signal. The target resistance control instruction instructs the heating element to increase the heating power to increase the ambient temperature. For example, the initial resistance of a resistor is 100 (Ω), the temperature change is 0.5 (℃), the humidity change is 2 (%), the temperature coefficient TCR is 0.01, the humidity coefficient HCR is 0.001, the correction coefficient K1 is 0.01, and K2 is 0.001. Substitute the formula to calculate the target resistance:

[0077]

[0078] After calculation, the target resistance is equal to 99.8Ω.

[0079] According to the scheme provided by the present invention, it includes an NTC resistor and a MOS tube, wherein the NTC resistor is connected to the gate of the MOS tube and is used to adjust the conduction state of the MOS tube by monitoring temperature changes; a voltage regulator circuit, whose input end is VCC and GND, and the output end is the S source, and the input ends VCC and GND provide power and ground wires for the circuit respectively; a PTC thermistor, connected to the S source of the MOS; wherein the input end of the NAND gate is provided with a first resistor, a second resistor, and a third resistor, wherein the first resistor is connected to the input end VCC, indicating a high level; the second resistor is connected to the input end VCC, and the third resistor is connected to another input end. The present invention does not directly read the NTC resistor voltage division value, but controls the on and off of the MOS tube by different voltage division values ​​of the NTC resistor at different temperatures to achieve heating control. It can be widely used in various camera devices that require heating and defrosting.

Claims

1. A camera automatic heating and defrosting system, characterized in that: include: An NTC resistor, which is connected to the gate of the MOS tube and is used to adjust the conduction state of the MOS tube by monitoring temperature changes; MOS tube, its input end is VCC and GND, the output end is S source, the input end VCC and GND provide power and ground for the whole circuit respectively; A PTC thermistor, i.e., a lens heating coil, is connected to the source of the MOS tube; Among them, the input end of the MOS tube is provided with a calibration resistor, an NTC resistor, and a PTC resistor, and the calibration resistor is connected to the input end voltage regulator, indicating a high level; the NTC resistor is connected to the gate of the MOS tube, and the PTC resistor is connected to the S source of the MOS tube; The resistance value of the PTC resistor is adjusted by a control instruction sent by the control system to the NAND gate circuit; The control system automatically generates a control instruction based on the monitored performance parameters of the NAND gate circuit and sends the control instruction to the NAND gate circuit; The control instructions include adjustment instructions and target resistance value control instructions; The calculation formula of the target resistance is: ； in, is the target resistance, is the initial resistance, is the temperature change, is the temperature coefficient of resistance, is the humidity change, is the humidity coefficient of resistance, and is the correction factor.

2. The camera automatic heating and defrosting system according to claim 1, characterized in that: The resistance of the PTC resistor is 100K.

3. The camera automatic heating and defrosting system according to claim 1, characterized in that: A feedback circuit is provided inside the voltage regulator circuit; When the output voltage increases or decreases, the feedback circuit adjusts the parameters of the internal components accordingly to keep the output voltage stable.

4. The camera automatic heating and defrosting system according to claim 1, characterized in that: The PTC resistor is used to heat the lens when the ambient temperature is lower than the lens surface temperature, so that the lens surface temperature is higher than the ambient temperature to avoid water vapor condensation on the lens surface; and stop heating when the lens surface temperature reaches a preset threshold to prevent the lens from overheating for a long time.

5. The camera automatic heating and defrosting system according to claim 1, characterized in that: The MOS tube controls the heating and stopping of the heating of the PTC resistor; Among them, when the gate-source voltage Vgs of the MOS tube is greater than the turn-on voltage threshold Vgsth value, the MOS tube is turned on and the PTC resistor starts to heat; when the gate-source voltage Vgs of the MOS tube is less than the Vgsth value, the MOS tube is disconnected and the PTC resistor stops heating.

6. The camera automatic heating and defrosting system according to claim 3, characterized in that: The feedback circuit includes a voltage detector and an error amplifier; The voltage detector is used to detect the change of the output voltage and transmit the detected voltage change signal to the error amplifier; The error amplifier adjusts the parameters of the internal components according to the voltage variation signal to control the stability of the output voltage.

7. The camera automatic heating and defrosting system according to claim 1, characterized in that: The calibration resistor and the NTC resistor are determined based on a heating parameter model.

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