CN202903330U - Ambient light detection circuit for camera - Google Patents

Abstract

The utility model discloses an ambient light detection circuit for a camera, which is mainly used for ambient light illuminance detection, and outputs a control signal, wherein the control signal can be used as a linkage signal for controlling the on and off of an infrared lamp, switching an optical filter and converting the day and night modes of the camera. The ambient light detection circuit comprises an ambient light detection module used for sensing ambient light and generating a corresponding detection signal, a time-delay module used for performing time-delay filtering on the detection signal generated by the ambient light detection module, and a driving module used for receiving the detection signal processed by the time-delay module and correspondingly generating a control signal for controlling the action of the camera. The ambient light detection circuit for a camera is simple in design, stable in performance, strong in flexibility, low in cost and strong in practicality; can avoid the conditions of mis-triggering the infrared lamp and the video image of the camera due to the existence of instantaneous light interference at night; and is suitable for a plurality of types of cameras.

Description

The ambient light detection circuit of video camera

Technical field

The utility model relates to technical field of video monitoring, particularly relates to a kind of ambient light detection circuit of video camera.

Background technology

Along with the development growth in monitoring field, video camera now all requirement can be realized round-the-clock monitoring, when night or ambient light are very low, need to have secondary light source to carry out light filling, and to belong to infrared light supply in the majority for secondary light source in the video camera market.When the external environment illuminance is very low, video camera can be opened infrared lamp automatically under light activated element control, but thermal camera in use, the back and forth situation of On/Off of infrared lamp can appear night, Ray Of Light is particularly arranged, such as the car light of night during automobile turning, flashlight light, neon glow etc., shine video camera and remove rapidly after, the reaction that the light activated element of video camera is made immediately can make infrared lamp the situation of false triggering occur, namely close again to the situation of opening by being opened to, video image also the situation that color/monochrome switches back and forth can occur thereupon, makes it not accepted by the client.

Summary of the invention

The purpose of this utility model is for the technological deficiency that exists in the prior art, and a kind of ambient light detection circuit of video camera is provided.

For realizing that the technical scheme that the purpose of this utility model adopts is:

A kind of ambient light detection circuit of video camera, comprise in order to the sensing external ambient light and produce the surround lighting detection module of corresponding detection signals, carry out the time delay module of filtering wave by prolonging time in order to the detection signal that described surround lighting detection module is produced, and the driver module that is used for receiving the control signal of the also corresponding generation control of the detection signal video camera action after time delay module is processed.

The hysteresis comparator circuit of described surround lighting detection module for being consisted of by operational amplifier.

Described time delay module is the RC time delay module, and it comprises the 5th resistance R 5 of connecting with described operational amplifier output pin and thesecond capacitor C 2 that is arranged on the 5th resistance R 5 rear portion earths.

Described driver module comprises a PNP triode Q1 and the 2nd NPN triode Q2, the base stage of described NPN triode Q2 is communicated with the output of time delay module, grounded emitter, collector is connected to the base stage of a PNP triode Q1 after the3rd resistance R 3, the collector of a described PNP triode Q1 is communicated to power supply+VCC, the base stage of a described PNP triode Q1 also is communicated with power supply+VCC through pull-up resistor thefirst resistance R 1 simultaneously, the emitter of a described PNP triode Q1 through successively the series connection the 4th resistance R 4 and the 8th resistance R 8 after ground connection, the output terminal of described driver module is connected between the 4th resistance R 4 and the 8th resistance R 8, and described output terminal can outwards be exported control signal.

Compared with prior art, the beneficial effects of the utility model are:

The utility model has increased time delay module, when the light that the short time occurs disturbs and the output that causes operational amplifier when becoming low level, thesecond capacitor C 2 discharges of time delay module can be kept the 2nd NPN triode Q2 maintenance conducting state that a period of time makes driver module, the control signal of output terminal remains high level, prevent from making immediately the output of driver module to change, this has just been avoided blink light to disturb the infrared lamp that causes and video image by false triggering, play a good buffer action, effectively guarantee product stability.

Description of drawings

Figure 1 shows that the ambient light detection circuit block scheme of video camera of the present utility model.

Embodiment

Below in conjunction with the drawings and specific embodiments the utility model is described in further detail.Should be appreciated that specific embodiment described herein only in order to explaining the utility model, and be not used in restriction the utility model.

As shown in Figure 1, the ambient light detection circuit of video camera of the present utility model, comprise in order to the sensing external ambient light and produce the surroundlighting detection module 1 of corresponding detection signals, carry out thetime delay module 2 of filtering wave by prolonging time in order to the detection signal that described surround lighting detection module is produced, and thedriver module 3 that is used for receiving the also corresponding control video camera action of detection signal after time delay module is processed.

Wherein, the hysteresis comparator circuit of described surround lighting detection module for being consisted of by operational amplifier U1, specifically, the input circuit of thenegative terminal pin 2 of described operational amplifier comprises power supply+VCC, thesecond resistance R 2,photosensitive resistor rp 1 and divider resistance R6, one end of wherein said thesecond resistance R 2 connects power supply+VCC, the other end is ground connection behind thephotosensitive resistor rp 1 of successively series connection and divider resistance R6, namely utilize photoresistance as the input of operational amplifier relatively to produce detection signal with the threshold voltage of setting.

Simultaneously, also be arranged in parallel thefirst capacitor C 1 at described divider resistance R6 two ends, the two ends of described the first electric capacity connect respectivelynegative terminal pin 2 and the place of working of operational amplifier U1.

The input circuit of theanode pin 3 of described operational amplifier comprises power supply+VCC, the 11 resistance R 11, the 7th resistance R 7, the 9th resistance R 9 and the tenth resistance R 10.Wherein, the 7th resistance R 7 one ends are connected the other end the 11 resistance R 11 rear ground connection of connecting with power supply+VCC, theoutput pin 1 of described the tenth resistance R 10 1 ends and operational amplifier is communicated with the other end connects and is connected between the 11 resistance R 11 and the 7th resistance R 7 behind the 9th resistance, and theanode pin 3 of described operational amplifier U1 is connected between the 9th resistance R 9 and the tenth resistance R 10.

Described time delay module is the RC time delay module, it comprises the 5th resistance R 5 of connecting with described operational amplifier output pin and thesecond capacitor C 2 that is arranged on the 5th resistance R 5 rear portion earths, at detection signal, when being the variation of high level or low level, utilize the effect that discharges and recharges of RC to realize the time-delay of high level, avoid in the short time driver module to receive the detection signal of variation.

Described driver module comprises a PNP triode Q1 and the 2nd NPN triode Q2, the base stage of described the 2nd NPN triode Q2 is communicated with the output of time delay module, its grounded emitter, collector is connected to the base stage of a PNP triode Q1 after the3rd resistance R 3, the collector of a described PNP triode Q1 is communicated to power supply+VCC, the base stage of a described PNP triode Q1 also is communicated with power supply+VCC through pull-up resistor thefirst resistance R 1 simultaneously, the emitter of a described PNP triode Q1 through successively the series connection the 4th resistance R 4 and the 8th resistance R 8 after ground connection, the output terminal of described driver module is connected between the 4th resistance R 4 and the 8th resistance R 8, described output terminal can outwards be exported control signal, and this control signal namely can be used as the driving circuit of infrared fileter, infrared lamp driving circuit and video camera be the interlock signal of change-over circuit day and night.Simultaneously, on described output terminal, also be provided with the3rd capacitor C 3, described the3rd capacitor C 3 one ends and output head grounding, other end ground connection is to provide the filtering protective effect.

Specifically when work, the variation of photoresistance causes that the input of operational amplifier positive and negative terminal pin changes, then cause exporting the variation of high-low level, wherein, operational amplifier output high level is to start driver module in the time of a little less than light, when the light that the short time occurs disturbs and the output that causes operational amplifier when becoming low level, thesecond capacitor C 2 discharges of time delay module can be kept the 2nd NPN triode Q2 maintenance conducting state that a period of time makes driver module, output terminal remains high level, prevent from making immediately the output of driver module to change, this has just been avoided blink light to disturb the infrared lamp that causes and video image by false triggering, play a good buffer action, effectively guarantee product stability.

In sum, the ambient light detection circuit of video camera of the present utility model, being mainly video camera provides the external environment illuminance to detect, export a control signal, control signal can be used as control infrared lamp open and close, optical filter switches, video camera is day and night changed interlock signal, its simplicity of design, stable, dirigibility is strong, cost is low, practical, the infrared lamp that can avoid light blink that video camera exists when night to disturb causing and video image are to be fit to the circuit that the polytype video camera uses by the situation of false triggering.

The above only is preferred implementation of the present utility model; should be noted that; for those skilled in the art; under the prerequisite that does not break away from the utility model principle; can also make some improvements and modifications, these improvements and modifications also should be considered as protection domain of the present utility model.

Claims (4)

1. the ambient light detection circuit of a video camera, it is characterized in that, comprise in order to the sensing external ambient light and produce the surround lighting detection module of corresponding detection signals, carry out the time delay module of filtering wave by prolonging time in order to the detection signal that described surround lighting detection module is produced, and the driver module that is used for receiving the control signal of the also corresponding generation control of the detection signal video camera action after time delay module is processed.

2. ambient light detection circuit as claimed in claim 1 is characterized in that, the hysteresis comparator circuit of described surround lighting detection module for being made of operational amplifier.

3. ambient light detection circuit as claimed in claim 1 or 2, it is characterized in that, described time delay module is the RC time delay module, and it comprises the 5th resistance R 5 of connecting with described operational amplifier output pin and the second capacitor C 2 that is arranged on the 5th resistance R 5 rear portion earths.

4. ambient light detection circuit as claimed in claim 3, it is characterized in that, described driver module comprises a PNP triode Q1 and the 2nd NPN triode Q2, the base stage of described NPN triode Q2 is communicated with the output of time delay module, grounded emitter, collector is connected to the base stage of a PNP triode Q1 after the 3rd resistance R 3, the collector of a described PNP triode Q1 is communicated to power supply+VCC, the base stage of a described PNP triode Q1 also is communicated with power supply+VCC through pull-up resistor the first resistance R 1 simultaneously, the emitter of a described PNP triode Q1 through successively the series connection the 4th resistance R 4 and the 8th resistance R 8 after ground connection, the output terminal of described driver module is connected between the 4th resistance R 4 and the 8th resistance R 8, and described output terminal can outwards be exported control signal.

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