Defogging and defrosting circuit for vehicle-mounted camera and camera

Abstract

The utility model discloses a demisting and defrosting circuit for a vehicle-mounted camera. The demisting and defrosting circuit comprises a control unit, a constant current source unit, a lens heating wire Rt and a temperature acquisition unit, the control unit is used for realizing level conversion of a control signal and outputting a heating signal; the constant current source unit is connected with the output end of the control unit, and the constant current source unit is configured to output a constant working current when receiving the heating signal; one end of the lens heating wire Rt is connected with the output end of the constant current source unit, constant working current is accessed, and the other end of the lens heating wire Rt is grounded; the temperature acquisition unit is installed at a position close to the lens heating wire Rt, and the temperature acquisition unit is configured to be used for acquiring the temperature value of the lens heating wire Rt. According to the utility model, the problems of fogging and frosting of the lens are solved through a heating mode, and the problem of overhigh heating temperature is avoided through a temperature detection mode.

Description

Technical Field

[0001] This utility model relates to the field of automotive technology, and in particular to a defogging and defrosting circuit for an in-vehicle camera. Background Technology

[0002] With the popularization and technological development of intelligent vehicles, most intelligent vehicles on the market now have in-vehicle imaging systems to assist drivers in parking and other driving operations. In-vehicle cameras are an indispensable component of these systems. In practice, during use in cold regions, fogging and frost can occur on the lenses due to low air temperatures. Under these conditions, the in-vehicle imaging system displays unclear images, and in severe cases, the image may be completely lost. This affects the driver's judgment and reduces overall vehicle safety. Therefore, developing a novel defogging and defrosting mechanism for in-vehicle cameras to overcome the aforementioned problems of existing technologies is a direction that requires further research by those skilled in the art. Utility Model Content

[0003] The purpose of this invention is to provide a defogging and defrosting circuit for vehicle cameras, which can overcome the problem of lens fogging and frosting by heating, and at the same time avoid the problem of excessive heating temperature by detecting the temperature.

[0004] This utility model discloses a defogging and defrosting circuit for an in-vehicle camera, which includes:

[0005] The control unit is used to perform level conversion of control signals and output heating signals;

[0006] A constant current source unit is connected to the output terminal of the control unit and is configured to output a constant operating current when the heating signal is received.

[0007] A lens heating wire Rt, one end of which is connected to the output terminal of the constant current source unit and connected to the constant operating current, and the other end of which is grounded;

[0008] A temperature acquisition unit is installed near the lens heating wire Rt and is configured to acquire the temperature value of the lens heating wire Rt.

[0009] This technical solution involves placing a lens heating wire Rt inside the vehicle-mounted camera. When the control unit outputs a heating signal, the constant current source unit outputs a constant operating current to the lens heating wire Rt, thereby powering on and heating it. The heated lens heating wire Rt then defrosts and removes fog from the vehicle-mounted camera lens. Simultaneously, a temperature acquisition unit collects the temperature value of the lens heating wire Rt, thus preventing the lens heating wire Rt from being continuously heated for too long through monitoring.

[0010] Preferably, the control unit includes:

[0011] The circuit consists of resistor R5, capacitor C3, resistor R6, NPN transistor Q2, and resistor R3. One end of resistor R5 is connected to signal port SC, and the other end is connected to the base of NPN transistor Q2. One end of capacitor C3 is connected to the base of NPN transistor Q2, and the other end is connected to the emitter of NPN transistor Q2. One end of resistor R6 is connected to the base of NPN transistor Q2, and the other end is connected to the emitter of NPN transistor Q2. The emitter of NPN transistor Q2 is grounded, and its collector is connected to one end of resistor R3.

[0012] The constant current source unit includes:

[0013] The circuit consists of a resistor R2, diodes D1 and D2, a PNP transistor Q1, and capacitors C1 and C2. The other end of resistor R3 is connected to one end of resistor R2, the cathode of diode D2, and the base of PNP transistor Q1. The other end of resistor R2 is connected to a +12V voltage, the anode of diode D1, one end of resistor R1, one end of capacitor C2, and one end of capacitor C1. The cathode of diode D1 is connected to the anode of diode D2. The other end of resistor R1 is connected to the emitter of PNP transistor Q1. The other end of capacitor C2 is connected to the other end of capacitor C1 and grounded.

[0014] One end of the lens heating wire Rt is connected to the collector of the PNP tube Q1, and the other end is grounded;

[0015] The temperature acquisition unit includes:

[0016] An NTC temperature sensor, resistors R4 and R7, and capacitor C4 are included. The NTC temperature sensor is positioned near the lens heating wire Rt. One end of the NTC temperature sensor is connected to one end of resistor R4 and one end of resistor R7, and the other end of the NTC temperature sensor is grounded. The other end of resistor R4 is connected to a +3.3V power supply. The other end of resistor R7 is connected to the ADC interface and one end of capacitor C4, and the other end of capacitor C4 is grounded.

[0017] Preferably, the resistance of resistor R5 is 1kΩ, the resistance of resistor R6 is 15kΩ, the capacitance of capacitor C3 is 1nF, and the resistance of resistor R3 is 1KΩ.

[0018] Preferably, the resistor R2 has a resistance of 15kΩ, the resistor R1 has a resistance of 2Ω, the diodes D1 and D2 are high-speed diodes 1N4148, the capacitor C2 has a capacitance of 100nF, and the capacitor C1 has a capacitance of 330μF.

[0019] Preferably, the resistance of resistor R4 is 10kΩ, the resistance of resistor R7 is 1kΩ, and the capacitance of capacitor C4 is 100nF.

[0020] Compared with the prior art, this utility model has a simple structure and is easy to manufacture. It can overcome the problems of lens fogging and frosting by heating, while also avoiding the problem of excessive heating temperature. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure of Example 1. Detailed Implementation

[0022] The following specific examples illustrate the implementation of this utility model. Those skilled in the art can easily understand other advantages and effects of this utility model from the content disclosed in this specification. This utility model can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this utility model.

[0023] This utility model discloses a defogging and defrosting circuit for an in-vehicle camera, which includes: a control unit, a constant current source unit, a lens heating wire Rt, and a temperature acquisition unit. Among them,

[0024] The control unit includes a resistor R5, a capacitor C3, a resistor R6, an NPN transistor Q2, and a resistor R3. The resistance of resistor R5 is 1kΩ, the resistance of resistor R6 is 15kΩ, the capacitance of capacitor C3 is 1nF, and the resistance of resistor R3 is 1kΩ. One end of resistor R5 is connected to the signal port SC, and the other end is connected to the base of the NPN transistor Q2. One end of capacitor C3 is connected to the base of the NPN transistor Q2, and the other end is connected to the emitter of the NPN transistor Q2. One end of resistor R6 is connected to the base of the NPN transistor Q2, and the other end is connected to the emitter of the NPN transistor Q2. The emitter of the NPN transistor Q2 is grounded, and its collector is connected to one end of resistor R3. The control unit is used to perform level conversion of the control signal and output a heating signal. The amplification factor Hfe2 of the NPN transistor Q2 is configured to be 100, the Ube of the NPN transistor Q2 is 0.6V, and the saturation voltage drop VCEsat of the NPN transistor Q2 is 0.7V.

[0025] The constant current source unit includes a resistor R2, a diode D1, a diode D2, a resistor R1, a PNP transistor Q1, a capacitor C1, and a capacitor C2; the resistance of the resistor R2 is 15kΩ, the resistance of the resistor R1 is 2Ω, the diodes D1 and D2 are high-speed diodes 1N4148; the capacitance of the capacitor C2 is 100nF, and the capacitance of the capacitor C1 is 330μF. One end of resistor R2 is connected to the other end of resistor R3, the cathode of diode D2, and the base of PNP transistor Q1. The other end of resistor R2 is connected to a +12V voltage, the anode of diode D1, one end of resistor R1, one end of capacitor C2, and one end of capacitor C1. The cathode of diode D1 is connected to the anode of diode D2. The other end of resistor R1 is connected to the emitter of PNP transistor Q1. The other end of capacitor C2 is connected to the other end of capacitor C1 and grounded. The constant current source unit is used to output a constant operating current when the heating signal is received. The amplification factor of PNP transistor Q1 is configured as Hfe1 = 80. The Ube of PNP transistor Q1 is 0.6V.

[0026] One end of the lens heating wire Rt is connected to the collector of the PNP tube Q1, and the other end is grounded; it is used to generate heat when the constant operating current is applied.

[0027] The temperature acquisition unit includes an NTC temperature sensor, resistors R4 and R7, and capacitor C4. Resistor R4 has a resistance of 10kΩ, resistor R7 has a resistance of 1kΩ, and capacitor C4 has a capacitance of 100nF. The NTC temperature sensor is positioned near the lens heating wire Rt. One end of the NTC temperature sensor is connected to one end of resistor R4 and one end of resistor R7, and the other end of the NTC temperature sensor is grounded. The other end of resistor R4 is connected to a +3.3V power supply. The other end of resistor R7 is connected to an ADC interface and one end of capacitor C4, and the other end of capacitor C4 is grounded. The temperature acquisition unit converts the temperature signal into a resistance signal that can be detected by the circuit.

[0028] In practice, its working process is as follows:

[0029] A 3.3V control signal is applied to the control unit via the signal port SC. Resistor R5 and capacitor C3 in the control unit together form a low-pass filter to filter out noise from the control signal. This circuit must ensure that the NPN transistor Q2 is in deep saturation. Therefore, the base current of NPN transistor Q2 is: Ib = (3.3 - Ube) ÷ R5 = 2.7V ÷ 1KΩ = 2.7mA. Since the amplification factor Hfe2 of NPN transistor Q2 is configured to 100, Ib × Hfe × R3 = 2.7 * 100 * 1 KΩ = 27V > 12V. At this point, NPN transistor Q2 is in deep saturation.

[0030] In the constant current source unit: when PNP transistor Q1 is in saturation conduction, NPN transistor Q2 is equivalent to switch S grounded. When PNP transistor Q1 is on, due to the presence of diodes D1 and D2, the Ub voltage is 10V (12-2×Ud=12-2×1=10V). The emitter current of Q1 is Is= (2-Ube)÷R1=(2-0.6V)÷2=0.7A. Due to the presence of diodes D1 and D2, the base b of PNP transistor Q1 and the positive voltage of the power supply are stabilized at 2V, Is= (2-Ube)÷R1. This allows for a stable current to be provided even under voltage fluctuation scenarios, thereby protecting the lens heating wire Rt, which serves as the subsequent load.

[0031] The temperature acquisition unit converts the acquired temperature value into a changing resistance signal. Resistor R4 is a voltage divider and current-limiting resistor, and resistor R7 and capacitor C4 together supply a low-pass filter with a cutoff frequency of 1 ÷ (2 × π × R7 × C4) = 1592 Hz. In practice, the cutoff frequency can be adjusted by adjusting the RC parameters.

[0032] The embodiments of this utility model have been described in detail above with reference to the accompanying drawings. However, this utility model is not limited to the above embodiments. Even if various changes are made to this utility model, if these changes fall within the scope of the claims of this utility model and their equivalents, they shall still fall within the protection scope of this utility model.

Claims

1. A vehicle camera defogging and defrosting circuit, characterized in that, include: The control unit is used to perform level conversion of control signals and output heating signals; A constant current source unit is connected to the output terminal of the control unit and is configured to output a constant operating current when the heating signal is received. A lens heating wire Rt, one end of which is connected to the output terminal of the constant current source unit and connected to the constant operating current, and the other end of which is grounded; A temperature acquisition unit is installed near the lens heating wire Rt and is configured to acquire the temperature value of the lens heating wire Rt.

2. The circuit according to claim 1, characterized in that, The control unit includes: The circuit consists of resistor R5, capacitor C3, resistor R6, NPN transistor Q2, and resistor R3. One end of resistor R5 is connected to signal port SC, and the other end is connected to the base of NPN transistor Q2. One end of capacitor C3 is connected to the base of NPN transistor Q2, and the other end is connected to the emitter of NPN transistor Q2. One end of resistor R6 is connected to the base of NPN transistor Q2, and the other end is connected to the emitter of NPN transistor Q2. The emitter of NPN transistor Q2 is grounded, and its collector is connected to one end of resistor R3. The constant current source unit includes: The circuit consists of a resistor R2, diodes D1 and D2, a PNP transistor Q1, and capacitors C1 and C2. The other end of resistor R3 is connected to one end of resistor R2, the cathode of diode D2, and the base of PNP transistor Q1. The other end of resistor R2 is connected to a +12V voltage, the anode of diode D1, one end of resistor R1, one end of capacitor C2, and one end of capacitor C1. The cathode of diode D1 is connected to the anode of diode D2. The other end of resistor R1 is connected to the emitter of PNP transistor Q1. The other end of capacitor C2 is connected to the other end of capacitor C1 and grounded. One end of the lens heating wire Rt is connected to the collector of the PNP tube Q1, and the other end is grounded; The temperature acquisition unit includes: An NTC temperature sensor, resistors R4 and R7, and capacitor C4 are included. The NTC temperature sensor is positioned near the lens heating wire Rt. One end of the NTC temperature sensor is connected to one end of resistor R4 and one end of resistor R7, and the other end of the NTC temperature sensor is grounded. The other end of resistor R4 is connected to a +3.3V power supply. The other end of resistor R7 is connected to the ADC interface and one end of capacitor C4, and the other end of capacitor C4 is grounded.

3. The circuit according to claim 2, characterized in that, The resistance of resistor R5 is 1kΩ, the resistance of resistor R6 is 15kΩ, the capacitance of capacitor C3 is 1nF, and the resistance of resistor R3 is 1KΩ.

4. The circuit according to claim 3, characterized in that, The resistor R2 has a resistance of 15kΩ, the resistor R1 has a resistance of 2Ω, the diodes D1 and D2 are high-speed diodes 1N4148, the capacitor C2 has a capacitance of 100nF, and the capacitor C1 has a capacitance of 330μF.

5. The circuit according to claim 4, characterized in that, The resistance of resistor R4 is 10kΩ, the resistance of resistor R7 is 1kΩ, and the capacitance of capacitor C4 is 100nF.

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