Circuit, method and device for controlling infrared lamp current

A technology of infrared lamps and voltage control, which is applied to the layout of lamp circuits, lighting devices, electric light sources, etc., can solve the problems of repeated restarts of infrared cameras, and achieve the effect of ensuring normal operation

Active Publication Date: 2016-02-17
HANGZHOU HIKVISION DIGITAL TECH
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AI-Extracted Technical Summary

Problems solved by technology

[0006] The present invention provides a control circuit, method and device for the current of an infrared lamp to at least solve the problem in the related art that w...
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Method used

[0039] In a preferred embodiment, the function of the choke circuit is to prevent the voltage of Vin from dropping due to the sudden and sharp rise of the cable current due to the opening of the infrared lamp. At the same time, the first resisto...
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Abstract

The invention discloses a circuit, a method and a device for controlling infrared lamp current. The circuit for controlling the infrared lamp current comprises a choke circuit, an MCU (micro control unit) circuit and an infrared lamp driving circuit, and is characterized in that the choke circuit is used for suppressing the variation amplitude of current of a cable which supplies power to the infrared camera when an infrared lamp inside an infrared camera is turned on; one input end of the MCU circuit is connected with a power supply inside the infrared camera, another input end of the MCU circuit is connected with the choke circuit, and an output end of the MCU circuit is connected with the infrared lamp driving circuit and is used for outputting control voltage under the suppression effect of the choke circuit for the variation amplitude, wherein the control voltage is used for controlling current flowing through the infrared lamp; and the infrared lamp driving circuit is connected with the MCU circuit and is used for regulating the current flowing through the infrared lamp according to the control voltage. According to the technical scheme provided by the invention, the infrared camera can adjust the turn-on power of the infrared lamp automatically according to impedance of the cable under the condition of long-distance power supply, thereby ensuring normal operations of the infrared camera.

Application Domain

Electric light circuit arrangement

Technology Topic

The chokesInfrared lamp +3

Image

  • Circuit, method and device for controlling infrared lamp current
  • Circuit, method and device for controlling infrared lamp current
  • Circuit, method and device for controlling infrared lamp current

Examples

  • Experimental program(1)

Example Embodiment

[0032] Hereinafter, the present invention will be described in detail with reference to the drawings and in conjunction with the embodiments. It should be noted that the embodiments in the application and the features in the embodiments can be combined with each other if there is no conflict.
[0033] In the following description, unless otherwise specified, each embodiment of the present application will be described with reference to symbolic representations of actions and operations performed by one or more computers. Among them, computers include various products such as personal computers, servers, and mobile terminals, and devices with processing chips such as central processing units (CPU), single-chip microcomputers, and digital signal processors (DSP) can all be called computers. From this, it can be understood that such actions and operations sometimes referred to as computer-executed include manipulation of electrical signals that represent data in a structured form by the processing unit of the computer. This manipulation transforms the data or maintains it at a location in the computer's memory system, which reconfigures or changes the operation of the computer in a manner understood by those skilled in the art. The data structure of the maintenance data is the physical location of the memory with specific attributes defined by the format of the data. However, although the present invention is described in the above context, it is not meant to be restrictive. As understood by those skilled in the art, the actions and aspects of operations described below can also be implemented by hardware.
[0034] Turning to the drawings, where the same reference numerals refer to the same elements, the principles of the present application are shown to be implemented in a suitable computing environment. The following description is based on the described embodiments of the present application, and should not be considered as limiting the present application with regard to alternative embodiments not explicitly described herein.
[0035] The following embodiments can be applied to a computer, for example: applied to a personal computer (PC). It can also be applied to mobile terminals currently using smart operating systems, and is not limited to this. There are no special requirements for the operating system of the computer or mobile terminal, as long as it can detect the contact, determine whether the contact meets the predetermined rules, and implement corresponding functions according to the attributes of the contact.
[0036] figure 1 It is a structural block diagram of an infrared lamp current control circuit according to an embodiment of the present invention. Such as figure 1 As shown, the infrared lamp current control circuit may include: a choke circuit 10, which is used to suppress the amplitude of change of the current through the cable that supplies power to the infrared camera when the infrared lamp inside the infrared camera is turned on; MCU circuit 20, One input end is connected to the power supply inside the infrared camera, the other input end is connected to the choke circuit 10, and the output end is connected to the infrared lamp driving circuit 30, which is used to suppress the amplitude of the change in the choke circuit Under the control voltage, the control voltage is used to control the current passing through the infrared lamp; the infrared lamp driving circuit 30 is connected to the MCU circuit 20 and is used to adjust the current flowing through the infrared lamp according to the control voltage.
[0037] In related technologies, when a long-distance cable is used to supply power to the infrared camera, it is easy to cause the infrared camera to restart repeatedly after turning on the infrared light. Use as figure 1 In the circuit shown, by adding a choke circuit inside the infrared camera, if a long-distance cable is used to power the infrared camera, then when the infrared lamp is turned on, the choke circuit is used to suppress the variation of the current through the cable. Eliminate instantaneous current spikes, and make the circuit flowing through the infrared lamp gradually rise, thus solving the problem of the infrared camera repeatedly restarting after turning on the infrared lamp when the infrared camera is powered by a long-distance cable in the related technology. , In the case of long-distance power supply, the infrared camera will automatically adjust the power of the infrared lamp according to the cable impedance, so as to ensure the normal operation of the infrared camera.
[0038] Preferably, figure 2 It is a schematic diagram of the device connection of the choke circuit according to the preferred embodiment of the present invention. Such as figure 2 As shown, the choke circuit 10 may include: a first resistor 100; an operational amplifier 102, the first input terminal of which is connected to the first resistor 100, the second input terminal and the output terminal form a closed loop, and the output terminal and the second resistor 104 The second resistor 104, one end of which is connected to the output terminal, and the other end of which is connected to one end of the capacitor 106; the capacitor 106, one end of which is connected to the second resistor 104, and the other end of which is connected to the first input terminal and the first A resistor 100 is connected.
[0039] In a preferred embodiment, the function of the choke circuit is to prevent the voltage of Vin from falling due to the sudden and sharp rise of the cable current when the infrared lamp is turned on. At the same time, the first resistor, the second resistor, and the capacitor can be properly valued to prevent the power frequency 50Hz interference on the cable from entering the infrared camera, thereby effectively preventing noise in the video image due to interference from the mains.
[0040] image 3 It is a flowchart of a method for controlling infrared lamp current according to an embodiment of the present invention. Such as image 3 As shown, the method may include the following processing steps:
[0041] Step S302: receiving a first voltage generated from a first power source, where the first power source is an internal power source of the infrared camera;
[0042] Step S304: Receive a second voltage from a second power source via a choke circuit, where the second power source is a power source for supplying power to the infrared camera through a cable of a preset length, and the choke circuit is used to turn on the internal infrared camera In the case of infrared light, suppress the change range of the current through the cable;
[0043] Step S306: Obtain the value range of the control voltage according to the first voltage and the second voltage, where the value range of the control voltage is used to control the current passing through the infrared lamp;
[0044] Step S308: Send the control voltage to the infrared lamp within the value range of the control voltage.
[0045] In related technologies, the causes of repeated restarts can be divided into the following two situations:
[0046] Reason 1. Because the current through the cable is too large when the infrared lamp is turned on, the voltage obtained by the power supply exceeds the minimum working voltage Vmin;
[0047] Reason 2: When the camera's infrared light is fully turned on, the power is insufficient, that is, Pn
[0048] Use as image 3 In the method shown, when the infrared light is not turned on, the infrared camera works normally and outputs the video signal. Once the infrared lamp is turned on, the instantaneous current generated on the cable is too large. By adding a choke circuit inside the infrared camera to eliminate the instantaneous current spike, the current will gradually rise when the infrared lamp is turned on, without the current spike.
[0049] Preferably, in step S306, obtaining the value range of the control voltage according to the first voltage and the second voltage may include the following operations:
[0050] Step S1: Calculate the DC impedance of the cable by using the first voltage, the second voltage and the first power, where the first power is the power of the infrared camera when the infrared light is not turned on;
[0051] Step S2: Calculate the second power according to the second voltage and the DC impedance, where the second power is the maximum power of the infrared camera and the second power is greater than the first power;
[0052] Step S3: Determine the value range of the control voltage through the first power and the second power.
[0053] Preferably, in step S1, calculating the DC impedance using the first voltage, the second voltage and the first power may include the following steps:
[0054] Step S11: Calculate the difference between the second voltage and the first voltage;
[0055] Step S12: Calculate the ratio of the first power to the first voltage;
[0056] Step S13: Divide the difference and the ratio to obtain the DC impedance.
[0057] Preferably, in step S2, calculating the second power according to the first voltage and DC impedance may include the following operations:
[0058] Step S21: Calculate the current through the cable by using the second voltage and the DC impedance;
[0059] Step S22: Multiply the current passing through the cable and the second voltage to obtain the second power.
[0060] The following will combine Figure 4 to Figure 8 The shown preferred embodiments further describe the above-mentioned preferred implementation process.
[0061] Figure 4 It is a schematic diagram of using a long-distance cable for power supply according to a preferred embodiment of the present invention. Such as Figure 4 As shown, if the long-distance method is used for power supply, then the loss that occurs on the cable must be considered at this time, that is, the DC impedance R of the power supply cable must be considered. The power of the infrared camera when it leaves the factory (including: under normal working conditions, the steady-state power of the infrared lamp is Pn (equivalent to the above-mentioned first power) and the total steady-state power of the infrared lamp Pr (equivalent to the above-mentioned The second power)) has been determined. Under normal circumstances, it is necessary to ensure that the power supply power P (voltage U) is greater than Pr.
[0062] Figure 5 Is based on the preferred embodiment of the present invention Figure 4 The equivalent schematic diagram of using long-distance cable for power supply. Such as Figure 5 As shown, when power is supplied from a long distance, the DC impedance R of the long-distance cable must be considered. If the DC impedance R is equivalent to the internal resistance of the power supply, the maximum power that the infrared camera can obtain is: Pmax=U^2/4R, so there is a possibility that Pmax cannot satisfy the condition greater than Pr. In this case, once the infrared light is turned on, the infrared camera will be powered off due to insufficient voltage. Under normal circumstances, Pmax is greater than Pn, otherwise even the basic video output function cannot be realized, so the infrared camera will get a power greater than Pn again, but once the infrared lamp is turned on again, it will get a power less than Pr. The infrared camera will restart continuously.
[0063] Image 6 It is a schematic diagram of a control frame inside an infrared camera according to a preferred embodiment of the present invention. Figure 7 It is a graph of infrared power controlled by MCU according to a preferred embodiment of the present invention. Such as Image 6 with Figure 7 As shown, the control method may include: analog dimming and pulse width modulation (PWM) dimming. The relevant power parameters involved in the operation of the infrared camera are built in the MCU circuit in advance, including but not limited to Pn, Pr, Pr=f(Vc) graphs, and the rated operating voltage of the infrared camera is the power supply voltage U. The MCU controls the relationship between U and Pr.
[0064] When the infrared light is not turned on, the infrared camera works normally and outputs video signals. Once the infrared lamp is turned on, the instantaneous current generated on the cable is too large, and the function of the choke circuit is to eliminate the instantaneous current spike, so that when the infrared lamp is turned on, the current gradually rises without the current spike. During normal operation, the MCU will detect the input voltage Vin input to the power module, and obtain the DC impedance of the power supply cable according to the following formula 1:
[0065] R=(U-Uin)/(Pn/Uin)……Formula 1;
[0066] The MCU can also calculate the maximum power that the infrared camera can obtain according to the following formula 2:
[0067] Pmax=U^2/4R……Formula 2;
[0068] At this time, the MCU can make Pr=Pmax according to the relationship diagram of Pr=f(Vc), and then obtain the corresponding voltage Vc for controlling the infrared lamp. Thus, the infrared light is activated within the power range of Pr.
[0069] After the infrared lamp driving circuit receives the Vc from the MCU circuit, it can control the current through the infrared lamp according to the magnitude of the Vc. Under any voltage Vi, the current value through the infrared lamp will vary from 0 to 100%.
[0070] Picture 8 It is a schematic structural diagram of an infrared lamp driving circuit according to a preferred embodiment of the present invention. Such as Picture 8 As shown, C0 is a filter capacitor, R0 is a current sampling resistor, LED is an infrared lamp, L is a freewheeling inductor, and D1 is a freewheeling diode. The principle is: in the case of preset Vi and Vc, use R0 to sample the current through the infrared lamp, and then compare with Vc, output a certain duty ratio PWM to close-loop control of the current through the infrared lamp.
[0071] Picture 9 It is a structural block diagram of an infrared lamp current control device according to an embodiment of the present invention. Such as Picture 9 As shown, the infrared lamp current control device may include: a first receiving module 90 for receiving a first voltage generated from a first power source, where the first power source is the power source inside the infrared camera; and a second receiving module 92 , Used to receive the second voltage from the second power supply via a choke circuit, where the second power supply is a power supply that supplies power to the infrared camera through a cable with a preset length, and the choke circuit is used to turn on the internal infrared camera In the case of an infrared lamp, the range of change of the current passing through the cable is suppressed; the obtaining module 94 is used to obtain the value range of the control voltage according to the first voltage and the second voltage, wherein the value range of the control voltage is used to control the infrared lamp The current; the sending module 96 is used to send the control voltage to the infrared lamp within the range of the control voltage.
[0072] Use as Picture 9 The shown device solves the problem that the infrared camera may restart repeatedly after turning on the infrared lamp when the infrared camera is powered by a long-distance cable in the related technology, and the infrared camera can be powered on a long distance. The power of turning on the infrared light is automatically adjusted according to the cable impedance to ensure the normal operation of the infrared camera.
[0073] Preferably, as Picture 10 As shown, the acquisition module 94 may include: a first calculation unit 940 for calculating the DC impedance of the cable using a first voltage, a second voltage, and a first power, where the first power is when the infrared camera is not turned on The second calculation unit 942 is used to calculate the second power according to the second voltage and DC impedance, where the second power is the maximum power of the infrared camera and the second power is greater than the first power; the determination unit 944 is used to pass The first power and the second power determine the value range of the control voltage.
[0074] Preferably, the first calculation unit 940 may include: a first calculation subunit (not shown in the figure) for calculating the difference between the second voltage and the first voltage; and a second calculation subunit (not shown in the figure) , Is used to calculate the ratio of the first power to the first voltage; the third calculation subunit (not shown in the figure) is used to divide the difference and the ratio to obtain the DC impedance.
[0075] Preferably, the second calculation unit 942 may include: a fourth calculation subunit (not shown in the figure) for calculating the current through the cable using the second voltage and DC impedance; and a fifth calculation subunit (not shown in the figure) Out), used to multiply the current through the cable and the second voltage to obtain the second power.
[0076] From the above description, it can be seen that the above-mentioned embodiments achieve the following technical effects (it should be noted that these effects are the effects that can be achieved by some preferred embodiments): The technical solutions provided by the embodiments of the present invention can be used in In the case of long-distance power supply, the infrared camera will automatically adjust the power of the infrared light according to the cable impedance to ensure the normal operation of the infrared camera.
[0077] Obviously, those skilled in the art should understand that the above-mentioned modules or steps of the present invention can be implemented by a general computing device, and they can be concentrated on a single computing device or distributed on a network composed of multiple computing devices. Above, alternatively, they can be implemented with program codes executable by the computing device, so that they can be stored in the storage device for execution by the computing device, and in some cases, can be executed in a different order than here. Perform the steps shown or described, or fabricate them into individual integrated circuit modules separately, or fabricate multiple modules or steps of them into a single integrated circuit module for implementation. In this way, the present invention is not limited to any specific combination of hardware and software.
[0078] The above are only preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various modifications and changes. Any modification, equivalent replacement, improvement, etc., made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

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