Constant current control circuit and method for machine vision light source

Abstract

The application provides a constant current control circuit for a machine vision light source, which is used for controlling an LED load and comprises a constant current drive chip U1, a triode Q1, an inductor L1 and a diode D2, a VIN pin of the constant current drive chip U1 is connected with a power supply through a first line, a PH pin of the constant current drive chip U1 is connected with one end of the inductor L1 through a second line, the other end of the inductor L1 is connected with the positive pole of the LED load through a ninth line, the ninth line is connected on the first line through a third line, the diode D2 is arranged on the third line, and the diode D2 makes the third line unidirectionally conduct from the ninth line to the first line; the negative pole of the LED load is connected on an ISENSE pin of the constant current drive chip U1 through a fourth line, and a resistor R2 is arranged on the fourth line; a fifth line is connected with an IADJ pin of the constant current drive chip U1, and the other end of the fifth line is used for connecting a controller, and the controller outputs a PWM signal.

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 machine vision light sources. Background Technology

[0002] With the widespread use of machine vision in various industries, achieving efficient current switching is of great significance. Conventionally, the current is adjusted manually or by a host computer, but the process is cumbersome and inefficient. To achieve efficient fixed current switching, a constant current switching circuit was designed. This circuit can also achieve multiple constant current switching through superposition, thereby improving the efficiency of rapidly changing the current. Summary of the Invention

[0003] The main objective of this invention is to provide a constant current control circuit and method for machine vision light sources, thereby achieving constant current control of machine vision light sources.

[0004] To achieve the above objectives, the technical solution adopted by this invention is: a constant current control circuit for machine vision light sources, used to control LED loads, comprising: a constant current driver chip U1, a transistor Q1, an inductor L1, and a diode D2. The VIN pin of the constant current driver chip U1 is connected to the power supply through the first line, and the PH pin of the constant current driver chip U1 is connected to one end of the inductor L1 through the second line. The other end of the inductor L1 is connected to the positive terminal of the LED load through the ninth line. The ninth line is connected to the first line through the third line. The diode D2 is placed on the third line, and the diode D2 makes the third line conduct unidirectionally from the ninth line to the first line. The negative terminal of the LED load is connected to the ISENSE pin of the constant current driver chip U1 through the fourth line, and a resistor R2 is placed on the fourth line. The IADJ pin of the constant current drive chip U1 is connected to a fifth line 5. The other end of the fifth line is used to connect to the controller, and the controller outputs a PWM signal.

[0005] Preferably, it also includes a seventh line, one end of which is connected to the 48V power supply and the other end is grounded. Resistors R1 and R6 are connected in series on the seventh line. The portion of the seventh line located between resistors R1 and R6 is connected to the UVLO pin of the constant current drive chip U1. The UVLO pin detects the voltage between resistors R1 and R6.

[0006] Preferably, it also includes an eighth line, one end of which is connected to the power supply and the other end is grounded. Resistors R8 and R11 are connected in series on the eighth line. The collector of transistor Q1 is connected to the PDIM pin of the constant current drive chip U1. The emitter of transistor Q1 is grounded. The base of transistor Q1 is connected to the portion of the eighth line located between resistors R8 and R11. At the same time, the portion of the eighth line located between resistors R8 and R11 is triggered by an external signal through the sixth line.

[0007] Preferably, the circuit also includes capacitors C6, C7, and C8, and resistor R7. Resistors R3, R4, and R5 are connected in series on the fifth line. One end of capacitor C6 is connected to the portion of the fifth line 5 between resistor R3 and the IADJ pin, and the other end of capacitor C6 is grounded. One end of capacitor C7 is connected to the portion of the fifth line 5 between resistor R3 and resistor R4, and the other end of capacitor C7 is grounded. One end of capacitor C8 is connected to the portion of the fifth line 5 between resistor R4 and resistor R5, and the other end of capacitor C8 is grounded. Resistor R7 is connected in parallel with capacitor C8. Resistors R3-R5, R7, and capacitors C6-C8 constitute a low-pass filter circuit, used to convert the PWM signal into a DC voltage signal. By changing the duty cycle of the PWM signal, the voltage value of the DC voltage signal can be changed.

[0008] Preferably, the circuit further includes a tenth line, one end of which is connected to the second line and the other end is grounded. A diode D3 is disposed on the tenth line, and the diode D3 conducts unidirectionally in the direction from ground to the second line.

[0009] The present invention also provides a constant current control method for a machine vision light source, specifically including the following steps: Step 1: Turn on all power supplies and set the duty cycle of the PWM signal in the controller; Step 2: When there is an external trigger signal, transistor Q1 is turned on, the voltage of the PDIM pin decreases, and the constant current drive chip U1 is turned on. Step 3: The PH pin outputs voltage, and the current flows sequentially through the second line, inductor L1, the ninth line, the LED load, the fourth line, the ISENSE pin, the GND pin, and ground. The LED load lights up, and at the same time, inductor L1 is charged and stored. Step 4: When the current through the ISENSE pin is less than or equal to the current reference value in the constant current driver chip U1, the constant current driver chip U1 is turned on, and step 3 is executed. Step 5: When the current passing through the ISENSE pin is greater than the current reference value in the constant current driver chip U1, the constant current driver chip U1 is disconnected, and step 6 is executed. Step Six: Inductor L1 discharges. Current flows from inductor L1, passing sequentially through the ninth line, the LED load, the fourth line, the ISENSE pin, the GND pin, and the tenth line, before returning to inductor L1. During this process, when the current passing through the ISENSE pin is less than or equal to the current reference value in the constant current driver chip U1, the constant current driver chip U1 is turned on, and Step Three is executed. When the current passing through the ISENSE pin is greater than the current reference value in the constant current driver chip U1, Step Six continues.

[0010] Compared with the prior art, the present invention has the following beneficial effects: This invention applies a constant current drive chip to the control of LED light sources, enabling constant current control of the LED light source and adjusting the duty cycle of the PWM signal as needed, ultimately achieving brightness adjustment of the LED light source. Attached Figure Description

[0011] Figure 1 This is a circuit schematic diagram according to the present invention. Detailed Implementation

[0012] 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.

[0013] like Figure 1 As shown, a constant current control circuit for machine vision light sources, used to control an LED load, includes a constant current driver chip U1, a transistor Q1, an inductor L1, and a diode D2. The constant current driver chip U1 is a TPS92512. The VIN pin of the constant current driver chip U1 is connected to a 48V power supply via a first line 1. The PH pin of the constant current driver chip U1 is connected to one end of the inductor L1 via a second line 2. The other end of the inductor L1 is connected to the positive terminal of the LED load via a ninth line 9. The ninth line 9 is connected to the first line 1 via a third line 3. The diode D2 is located on the third line 3, causing the third line 3 to conduct unidirectionally from the ninth line 9 to the first line 1. The negative terminal of the LED load is connected to the ISENSE pin of the constant current driver chip U1 via a fourth line 4, and a resistor R2 is located on the fourth line 4.

[0014] The control circuit also includes a seventh line 7 and an eighth line 8. One end of the seventh line 7 is connected to the 48V power supply, and the other end is grounded. Resistors R1 and R6 are connected in series on the seventh line 7. The portion of the seventh line 7 located between resistors R1 and R6 is connected to the UVLO pin of the constant current drive chip U1. The UVLO pin detects the voltage between resistors R1 and R6. When the power supply voltage is too low, the voltage of the UVLO pin is lower than a predetermined value. At this time, the constant current drive chip U1 is in the off state, and the PH pin no longer outputs.

[0015] One end of the eighth line 8 is connected to the 48V power supply, and the other end is grounded. Resistors R8 and R11 are connected in series on the eighth line 8. The collector of transistor Q1 is connected to the PDIM pin of the constant current driver chip U1, the emitter of transistor Q1 is grounded, and the base of transistor Q1 is connected to the portion of the eighth line 8 located between resistors R8 and R11. Simultaneously, the portion of the eighth line 8 located between resistors R8 and R11 is connected to an external trigger signal via the sixth line 6. The base voltage of transistor Q1 is the sum of the voltage across the eighth line 8 between resistors R8 and R11 and the voltage of the external trigger signal. Thus, the external trigger signal can control the on / off state of transistor Q1 with a relatively small voltage. When the external trigger signal is low, transistor Q1 is off, the PDIM pin is high, the constant current driver chip U1 is off, and the PH pin no longer outputs. When the external trigger signal is high, transistor Q1 is on, the PDIM pin is low, the constant current driver chip U1 is on, and the PH pin outputs a voltage. The external trigger signal can be the positioning signal of the workpiece being detected.

[0016] The constant current driver chip U1 has its IADJ pin connected to a fifth line 5. The other end of this fifth line is connected to a controller, which outputs a PWM signal. Resistors R3, R4, and R5 are connected in series on the fifth line 5. The circuit also includes capacitors C6, C7, and C8, and resistor R7. One end of capacitor C6 is connected to the portion of the fifth line 5 between resistor R3 and the IADJ pin, and the other end is grounded. One end of capacitor C7 is connected to the portion of the fifth line 5 between resistors R3 and R4, and the other end is grounded. One end of capacitor C8 is connected to the portion of the fifth line 5 between resistors R4 and R5, and the other end is grounded. Resistor R7 is connected in parallel with capacitor C8. Resistors R3-R5, R7, and capacitors C6-C8 constitute a low-pass filter circuit, used to convert the PWM signal into a DC voltage signal. By changing the duty cycle of the PWM signal, the voltage value of the DC voltage signal can be changed. When the voltage value of the IADJ pin changes, the current value passing through it will also change. By changing the current value, the current reference value inside the constant current driver chip U1 can be adjusted. The current reference value is a characteristic of the constant current driver chip U1.

[0017] The ISENSE pin is used to detect the current on line 4 and compare it with a current reference value. This comparison controls the on / off state of the constant current driver chip U1, thereby controlling the brightness of the LED light source. Changing the duty cycle of the PWM signal alters the current reference value within the constant current driver chip U1. Once the PWM signal is determined, the current reference value within the constant current driver chip U1 is established, resulting in a constant current output to the LED load, achieving constant current control.

[0018] The circuit also includes a tenth line 10, one end of which is connected to the second line 2, and the other end is grounded. A diode D3 is disposed on the tenth line 10, and the diode D3 conducts unidirectionally in the direction from ground to the second line 2.

[0019] The working principle of this circuit is as follows: When U1 is turned on, the 48V power supply powers U1. The voltage required by the LED comes out from the PH pin, passes through inductor L1, LED+, LED load, LED-, resistor R2, ISENSE pin, and GND pin. When the 48V power supply powers the LED load, it also charges inductor L.

[0020] When U2 is disconnected, the PH pin no longer outputs voltage, and inductor L1 begins to discharge. The current of inductor L1 flows sequentially through LED+, the load, LED-, the ISENSE pin, the GND pin, the tenth line 10, and the other end of inductor L1. Even when U2 is disconnected, the normal operation of the LED load is still ensured through inductor L1.

[0021] When inductor L1 is discharging, if the inductance is higher than 48V, a portion of the voltage will return to the VIN pin through the third line 3, achieving rapid discharge and avoiding damage to the LED load.

[0022] 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 machine vision light sources, used to control an LED load, characterized in that, include: Constant current driver chip U1, transistor Q1, inductor L1, diode D2, The VIN pin of the constant current driver chip U1 is connected to the power supply through the first line, and the PH pin of the constant current driver chip U1 is connected to one end of the inductor L1 through the second line. The other end of the inductor L1 is connected to the positive terminal of the LED load through the ninth line. The ninth line is connected to the first line through the third line. The diode D2 is placed on the third line, and the diode D2 makes the third line conduct unidirectionally from the ninth line to the first line. The negative terminal of the LED load is connected to the ISENSE pin of the constant current driver chip U1 through the fourth line, and a resistor R2 is placed on the fourth line. The IADJ pin of the constant current drive chip U1 is connected to a fifth line 5. The other end of the fifth line is used to connect to the controller, and the controller outputs a PWM signal.

2. The constant current control circuit for a machine vision light source according to claim 1, characterized in that, It also includes a seventh line, one end of which is connected to the 48V power supply and the other end is grounded. Resistors R1 and R6 are connected in series on the seventh line. The portion of the seventh line located between resistors R1 and R6 is connected to the UVLO pin of the constant current drive chip U1. The UVLO pin detects the voltage between resistors R1 and R6.

3. The constant current control circuit for a machine vision light source according to claim 2, characterized in that, It also includes an eighth line, one end of which is connected to the power supply and the other end is grounded. Resistors R8 and R11 are connected in series on the eighth line. The collector of transistor Q1 is connected to the PDIM pin of the constant current drive chip U1. The emitter of transistor Q1 is grounded. The base of transistor Q1 is connected to the portion of the eighth line located between resistors R8 and R11. At the same time, the portion of the eighth line located between resistors R8 and R11 is triggered by an external signal through the sixth line.

4. The constant current control circuit for a machine vision light source according to claim 3, characterized in that, It also includes capacitors C6, C7, and C8, and resistor R7. Resistors R3, R4, and R5 are connected in series on the fifth line. One end of capacitor C6 is connected to the portion of the fifth line 5 between resistor R3 and the IADJ pin, and the other end of capacitor C6 is grounded. One end of capacitor C7 is connected to the portion of the fifth line 5 between resistors R3 and R4, and the other end of capacitor C7 is grounded. One end of capacitor C8 is connected to the portion of the fifth line 5 between resistors R4 and R5, and the other end of capacitor C8 is grounded. Resistor R7 is connected in parallel with capacitor C8. Resistors R3-R5, R7, and capacitors C6-C8 constitute a low-pass filter circuit, used to convert the PWM signal into a DC voltage signal. By changing the duty cycle of the PWM signal, the voltage value of the DC voltage signal can be changed.

5. A constant current control circuit for a machine vision light source according to claim 4, characterized in that, The circuit also includes a tenth line, one end of which is connected to the second line and the other end is grounded. A diode D3 is disposed on the tenth line, and the diode D3 conducts unidirectionally in the direction from ground to the second line.

6. A constant current control method for a machine vision light source, specifically comprising the following steps: Step 1: Turn on all power supplies and set the duty cycle of the PWM signal in the controller; Step 2: When there is an external trigger signal, transistor Q1 is turned on, the voltage of the PDIM pin decreases, and the constant current drive chip U1 is turned on. Step 3: The PH pin outputs voltage, and the current flows sequentially through the second line, inductor L1, the ninth line, the LED load, the fourth line, the ISENSE pin, the GND pin, and ground. The LED load lights up, and at the same time, inductor L1 is charged and stored. Step 4: When the current through the ISENSE pin is less than or equal to the current reference value in the constant current driver chip U1, the constant current driver chip U1 is turned on, and step 3 is executed. Step 5: When the current passing through the ISENSE pin is greater than the current reference value in the constant current driver chip U1, the constant current driver chip U1 is disconnected, and step 6 is executed. Step Six: Inductor L1 discharges. Current flows from inductor L1, passing sequentially through the ninth line, the LED load, the fourth line, the ISENSE pin, the GND pin, and the tenth line, before returning to inductor L1. During this process, when the current passing through the ISENSE pin is less than or equal to the current reference value in the constant current driver chip U1, the constant current driver chip U1 is turned on, and Step Three is executed. When the current passing through the ISENSE pin is greater than the current reference value in the constant current driver chip U1, Step Six continues.

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