Light source constant current control circuit and method for machine vision

Abstract

The invention provides a light source constant-current control circuit for machine vision, and the circuit comprises a step-down constant-current chip of which the DIM pin is connected with a controller through a first line and is used for receiving a PWM signal outputted by the controller, the VIN pin is connected with a power supply through a second line, the CSN pin is connected to the second line through a third line, and the third line is provided with a resistor R15; the part, located between the resistor R15 and the CSN pin, of the third circuit is connected to a pin 2 of the wiring terminal P4 through a fourth circuit, the pin 2 is used for being connected with the positive electrode of an LED light source, a pin 3 of the wiring terminal P4 is electrically connected with an SW pin of the step-down constant-current circuit U6 through a fifth circuit, and an inductor L2 is arranged on the fifth circuit; and the diode D8 is arranged on the sixth line, the part, located between the inductor L2 and the SW pin, of the fifth line is connected with the second line through the sixth line, and the diode D8 is configured to be in one-way conduction from the fifth line to the second line.

Description

Technical Field

[0001] This invention relates to the field of machine vision, and more particularly to a constant current control circuit and method for a light source used in machine vision. Background Technology

[0002] Machine vision is already very common in industrial production. It can be used to detect and locate products in real time. Specifically, machine vision involves taking pictures and then processing them. When taking pictures, a light source is required, and different scenes require different light sources. Under the same scene, the light source needs to be kept stable. Summary of the Invention

[0003] The main objective of this invention is to provide a constant current control circuit and method for a light source in machine vision, which can achieve constant current control of the light source.

[0004] To achieve the above objectives, the technical solution adopted by this invention is: a constant current control circuit for a light source in machine vision, comprising: The step-down constant current chip has its DIM pin connected to the controller through the first line to receive the PWM signal output by the controller, its VIN pin connected to the power supply through the second line, and its CSN pin connected to the second line through the third line. A resistor R15 is set on the third line. Terminal P4, the portion of the third line located between resistor R15 and CSN pin is connected to pin 2 of terminal P4 via a fourth line. Pin 2 is used to connect to the positive terminal of the LED light source. Pin 3 of terminal P4 is electrically connected to the SW pin of the step-down constant current circuit U6 via a fifth line. An inductor L2 is provided on the fifth line. Diode D8 is located on the sixth line. The portion of the fifth line located between the inductor L2 and the SW pin is connected to the second line through the sixth line. Diode D8 is configured to conduct unidirectionally from the fifth line to the second line.

[0005] Preferably, the circuit further includes capacitors C21, C22, and C23. Resistors R12, R13, and R14 are sequentially arranged along the direction of current on the first line. One end of capacitor C21 is connected to the portion of the first line between resistors R12 and R13, and the other end of capacitor C21 is grounded. One end of capacitor C22 is connected to the portion of the first line between resistors R13 and R14, and the other end of capacitor C22 is grounded. One end of resistor C23 is connected to the portion of the first line between resistor R14 and pin DIM, and the other end of capacitor C23 is grounded.

[0006] The present invention also provides a constant current control method for a light source for machine vision, which specifically includes the following steps: Step 1: The controller outputs a PWM signal as required; Step 2: The PWM signal is processed by resistors R12, R13, and R14, and capacitors C21, C22, and C23, and converted into an analog signal that enters the DIM pin of the step-down constant current chip U6. Step 3: The step-down constant current chip U6 adjusts the duty cycle by controlling the switch of the SW pin based on the current input from the DIM pin, thereby changing the current through the light source and enabling the light source to reach the predetermined brightness. Step 4: When the SW pin is turned on, the current flows from the power supply through resistor R15, the fourth line, the positive terminal of the light source, the negative terminal of the light source, inductor L2, the SW pin, and the ground terminal in sequence, charging inductor L2 during this process. Step 5: When the SW pin is turned off, inductor L2 discharges. When the voltage of inductor L2 during discharge exceeds the power supply voltage, current flows from inductor L2, through diode D8, resistor R15, the positive terminal of the power supply, the negative terminal of the power supply, and back to inductor L2. When the voltage of inductor L2 during discharge does not exceed the power supply voltage, no current flows through the light source.

[0007] Compared with the prior art, the present invention has the following beneficial effects: This invention enables constant current control of the light source. Attached Figure Description

[0008] Figure 1 This is a circuit diagram for a low-pass filter; Figure 2 This is a circuit diagram related to a step-down constant current chip; Figure 3 This is a circuit diagram related to the wiring terminals. Detailed Implementation

[0009] The following description is intended to disclose the invention and enable those skilled in the art to implement it. The preferred embodiments described below are merely examples, and other obvious variations will occur to those skilled in the art.

[0010] A constant current control circuit for a light source for machine vision includes a step-down constant current chip U6 and a terminal block P4. The step-down constant current chip U6 is a PT4115. The DIM pin of the step-down constant current chip U6 is connected to a controller through a first line 1 to receive the PWM signal output by the controller. Resistors R12, R13, and R14 are sequentially arranged along the direction of current on the first line 1. The circuit also includes capacitors C21, C22, and C23. One end of capacitor C21 is connected to the portion of the first line between resistors R12 and R13, and the other end of capacitor C21 is grounded. One end of capacitor C22 is connected to the portion of the first line between resistors R13 and R14, and the other end of capacitor C22 is grounded. One end of resistor C23 is connected to the portion of the first line between resistor R14 and pin DIM, and the other end of capacitor C23 is grounded. Through resistors R12, R13, R14, and capacitors C21, C22, and C23, the PWM signal can be converted into an analog signal.

[0011] The VIN pin of the step-down constant current chip U6 is connected to the driving power supply via the second line 2, which provides power for the LED light source. The CSN pin of the step-down constant current chip U6 is connected to the second line 2 via the third line 3. A resistor R15 is also provided on the third line 3. The portion of the third line 3 between the resistor R15 and the CSN pin is connected to pin 2 of the terminal P4 via the fourth line 4. Pin 2 is used to connect to the positive terminal of the LED light source. Pin 3 of the terminal P4 is electrically connected to the SW pin of the step-down constant current circuit U6 via the fifth line 5. An inductor L2 is provided on the fifth line 5. The portion of the fifth line 5 between the inductor L2 and the SW pin is connected to the second line 2 via the sixth line 6. A diode D8 is provided on the sixth line 6, and the diode D8 is configured to conduct unidirectionally from the fifth line 5 to the second line 2.

[0012] The circuit also includes capacitors C19 and C20, which are connected in parallel, with one end connected to the second line 2 and the other end grounded.

[0013] The working principle of this invention is as follows: The controller outputs a PWM signal. When the PWM signal passes through resistors R12, R13, R14 and capacitors C21, C22, and C23, it is converted into an analog signal and enters the DIM pin of the step-down constant current chip U6. After receiving the input voltage signal at the DIM pin, the step-down constant current chip U6 adjusts the duty cycle of its internal MOS transistor according to the received voltage signal.

[0014] The CSN of the buck constant current chip U6 can collect the voltage passing through R15 in real time. The voltage and resistance value collected by resistor R15 can be used to calculate the current passing through the light source. When the current deviates from the predetermined value, the buck constant current chip U6 will automatically adjust the duty cycle of switch SW to change the magnitude of the current.

[0015] When the MOSFET is turned on, the current flows through the drive power supply, the second line 2, the third line 3, the LED light source, the fifth line 5, and the SW pin. When the MOSFET is turned off, the inductor L2 releases electrical energy, and the current flows through the inductor L2, diode D8, R15, the LED light source, and finally back to the inductor L2. At this time, the circuit can only work normally when the voltage of the inductor L2 exceeds the voltage of the power supply.

[0016] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention. The scope of protection claimed by the appended claims and their equivalents is defined.

Claims

1. A constant current control circuit for a light source used in machine vision, characterized in that, include: The step-down constant current chip has its DIM pin connected to the controller through the first line to receive the PWM signal output by the controller, its VIN pin connected to the power supply through the second line, and its CSN pin connected to the second line through the third line. A resistor R15 is set on the third line. Terminal P4, the portion of the third line located between resistor R15 and CSN pin is connected to pin 2 of terminal P4 via a fourth line. Pin 2 is used to connect to the positive terminal of the LED light source. Pin 3 of terminal P4 is electrically connected to the SW pin of the step-down constant current circuit U6 via a fifth line. An inductor L2 is provided on the fifth line. Diode D8 is located on the sixth line. The portion of the fifth line located between the inductor L2 and the SW pin is connected to the second line through the sixth line. Diode D8 is configured to conduct unidirectionally from the fifth line to the second line.

2. The constant current control circuit for a light source in machine vision according to claim 1, characterized in that, It also includes capacitors C21, C22, and C23. Resistors R12, R13, and R14 are sequentially arranged along the direction of current on the first line. One end of capacitor C21 is connected to the portion of the first line between resistors R12 and R13, and the other end of capacitor C21 is grounded. One end of capacitor C22 is connected to the portion of the first line between resistors R13 and R14, and the other end of capacitor C22 is grounded. One end of resistor C23 is connected to the portion of the first line between resistor R14 and pin DIM, and the other end of capacitor C23 is grounded.

3. A constant current control method for a light source in machine vision, employing the constant current control circuit for a light source in machine vision as described in claim 2, characterized in that, Specifically, the steps include the following: Step 1: The controller outputs a PWM signal as required; Step 2: The PWM signal is processed by resistors R12, R13, and R14, and capacitors C21, C22, and C23, and converted into an analog signal that enters the DIM pin of the step-down constant current chip U6. Step 3: The step-down constant current chip U6 adjusts the duty cycle by controlling the switch of the SW pin based on the current input from the DIM pin, thereby changing the current through the light source and enabling the light source to reach the predetermined brightness. Step 4: When the SW pin is turned on, the current flows from the power supply through resistor R15, the fourth line, the positive terminal of the light source, the negative terminal of the light source, inductor L2, the SW pin, and the ground terminal in sequence, charging inductor L2 during this process. Step 5: When the SW pin is turned off, inductor L2 discharges. When the voltage of inductor L2 during discharge exceeds the power supply voltage, current flows from inductor L2, through diode D8, resistor R15, the positive terminal of the power supply, the negative terminal of the power supply, and back to inductor L2. When the voltage of inductor L2 during discharge does not exceed the power supply voltage, no current flows through the light source.

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