LED constant current driving controller with wide load response

Abstract

The utility model relates to an LED constant current driving controller with wide load response, which comprises a PWM control chip, a driving circuit 1, a power tube Q1, an inductor L1, a capacitor C1, a voltage detection circuit, a power tube Q2, a driving circuit 2, a load interface, a load detection circuit, a CPU, a digital point locator, a multistage amplifier and a current detection resistor R1, and is characterized in that the PWM control chip is electrically connected with the left end of the driving circuit 1. According to the technical scheme, the brightness adjustment range can be widened, the brightness response curve is close to linearity as much as possible, current adjustment is more accurate, and user experience is better; the controller of one model can drive loads of more models at the same time, and especially when multiple LED light sources are used by one device, the application cost of customers is reduced to a certain extent.

Description

Technical Field

[0001] The utility model relates to the technical field of LED driving, in particular to an LED constant current driving controller with wide load response. Background Art

[0002] Machine vision has brought revolutionary changes to industrial production. In traditional factory production, a lot of manpower is required for inspection and quality control. With the development of machine vision, we can use smart cameras and image processing algorithms to achieve automated quality inspection. This not only improves production efficiency, but also reduces the possibility of human error. In industrial applications, in order to provide stable lighting for the camera, the LED light source is usually driven by constant current.

[0003] There are generally two ways to drive LED constant current. One is to control the conduction depth of the power tube by detecting the size of the load current, and the power tube works in a linear amplification state. The power tube loss of this type of circuit is relatively large, the heat is large, and the efficiency is low. It is generally suitable for low-power applications. The other is to control the on-time and off-time ratio of the power tube by detecting the size of the load current, that is, the PWM control method. The power tube works in two states: saturated conduction and complete cutoff, which is equivalent to the on and off of a mechanical switch. The power tube loss of this type of circuit is greatly reduced, the heat is effectively controlled, the efficiency is high, and it can be used in high-power applications. Both circuits involve a current detection link. This is the key to achieving constant current.

[0004] The traditional LED driving circuit has a simple structure and a concise circuit, but it has the following disadvantages:

[0005] (1) In this type of circuit, the brightness control range is relatively small, and when the duty cycle of PWM2 that controls the brightness is changed, the brightness of the LED does not increase or decrease in equal proportion, that is, the brightness response curve is relatively curved.

[0006] (2) When dealing with different loads, this type of circuit is difficult to adapt and cannot conveniently achieve the situation where one controller drives multiple loads, which increases the customer's application cost. Utility Model Content

[0007] 1. Technical issues to be solved

[0008] In order to solve the above technical problems, the utility model provides an LED constant current drive controller with wide load response.

[0009] (II) Technical solution

[0010] Based on this, the utility model provides the following technical solutions: a wide load response LED constant current drive controller, including a PWM control chip, a drive circuit 1, a power tube Q1, an inductor L1, a capacitor C1, a voltage detection circuit, a power tube Q2, a drive circuit 2, a load interface, a load detection circuit, a CPU, a digital positioner, a multi-stage amplifier, and a current detection resistor R1. The PWM control chip is electrically connected to the left end of the drive circuit 1. The PWM control chip generates a PWM signal output to the drive circuit 1 by detecting the input of the multi-stage amplifier and the voltage detection circuit, so as to control the conduction and cutoff of the power tube Q1;

[0011] The drive circuit 1 is electrically connected to the pin No. 1 of the power tube Q1, the pin No. 3 of the power tube Q1 is electrically connected to the inductor L1, the lower end of the inductor L1 is electrically connected to the capacitor C1, the inductor L1 is connected to the lower end of the voltage detection circuit, the connection point between the inductor L1 and the pin No. 2 of the power tube Q2 is set as point A, and the connection point between the pin No. 3 of the load interface and the current detection resistor R1 and the multi-stage amplifier is set with point B;

[0012] The voltage detection circuit is electrically connected to pin No. 2 of the power tube Q2, pin No. 1 of the power tube Q2 is connected to the drive circuit 2, the drive circuit 2 is connected to the right end of the CPU, the voltage detection circuit is electrically connected to the right end of the PWM control chip, pin No. 3 of the power tube Q2 is electrically connected to pin No. 1 of the load interface, pin No. 2 of the load interface is electrically connected to the load detection circuit, the load detection circuit will continuously detect whether a load is connected to the load interface and the model of the load at intervals, the load detection circuit is connected to the CPU, pin No. 3 of the load interface is electrically connected to the current detection resistor R1, the current detection resistor R1 is electrically connected to the multi-stage amplifier, the multi-stage amplifier is electrically connected to the lower end of the digital position indicator, and the upper end of the digital position indicator is electrically connected to the CPU.

[0013] Preferably, the connection point between pin 3 of the power tube Q1 and the inductor L1 is connected to pin 2 of the diode D1, and pin 1 of the diode D1 is connected to the ground terminal GND.

[0014] Preferably, the left end of the capacitor C1 is connected to the ground terminal GND.

[0015] Preferably, pin 2 of the power tube Q1 is connected to a 24V power supply.

[0016] Preferably, the lower end of the current detection resistor R1 is connected to a ground terminal GND.

[0017] Preferably, a variable resistor VR is connected to the lower end of the multi-stage amplifier, and the resistance of the variable resistor VR is 10K.

[0018] Preferably, the left end of the variable resistor VR is connected to VCC5, and the right end of the variable resistor VR is connected to the ground terminal GND.

[0019] (III) Beneficial effects

[0020] Compared with the prior art, the utility model provides a LED constant current drive controller with a wide load response, which has the following beneficial effects:

[0021] This is an LED constant current drive controller with a wide load response. The technical solution can broaden the brightness adjustment range, make the brightness response curve as close to linear as possible, make the current adjustment more precise, and provide a better user experience; it enables one model of controller to drive more models of loads at the same time, especially when one device uses multiple LED light sources, thereby reducing the customer's application cost to a certain extent. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is the circuit principle block diagram of the utility model;

[0023] Figure 2 This is the circuit diagram of the PWM control chip of the utility model;

[0024] Figure 3 This is the power tube circuit diagram of the utility model;

[0025] Figure 4 This is the channel selection and CPU processing circuit diagram of the utility model;

[0026] Figure 5 This is the brightness adjustment and digital potentiometer circuit diagram of the utility model;

[0027] Figure 6 This is a multi-stage amplifier circuit diagram of the utility model.

[0028] In the figure: PWM control chip, drive circuit 1, power tube Q1, inductor L1, capacitor C1, voltage detection circuit, power tube Q2, drive circuit 2, load interface, load detection circuit, CPU, digital positioner, multi-stage amplifier, current detection resistor R1, variable resistor VR, diode D1. DETAILED DESCRIPTION

[0029] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0030] Example 1

[0031] See also Figure 1 , a wide load response LED constant current drive controller, including a PWM control chip, a drive circuit 1, a power tube Q1, an inductor L1, a capacitor C1, a voltage detection circuit, a power tube Q2, a drive circuit 2, a load interface, a load detection circuit, a CPU, a digital positioner, a multi-stage amplifier, and a current detection resistor R1, wherein the PWM control chip is electrically connected to the left end of the drive circuit 1, and the PWM control chip generates a PWM signal and outputs it to the drive circuit 1 by detecting the input of the multi-stage amplifier and the voltage detection circuit to control the conduction and cutoff of the power tube Q1; the drive circuit 1 is electrically connected to pin No. 1 of the power tube Q1, pin No. 3 of the power tube Q1 is electrically connected to the inductor L1, the lower end of the inductor L1 is electrically connected to the capacitor C1, and the inductor L1 is connected to the lower end of the voltage detection circuit; The voltage detection circuit is electrically connected to pin No. 2 of the power tube Q2, pin No. 1 of the power tube Q2 is connected to the drive circuit 2, the drive circuit 2 is connected to the right end of the CPU, the voltage detection circuit is electrically connected to the right end of the PWM control chip, pin No. 3 of the power tube Q2 is electrically connected to pin No. 1 of the load interface, pin No. 2 of the load interface is electrically connected to the load detection circuit, the load detection circuit will continuously detect whether a load is connected to the load interface and the model of the load at intervals, the load detection circuit is connected to the CPU, pin No. 3 of the load interface is electrically connected to the current detection resistor R1, the current detection resistor R1 is electrically connected to the multi-stage amplifier, the multi-stage amplifier is electrically connected to the lower end of the digital position indicator, and the upper end of the digital position indicator is electrically connected to the CPU.

[0032] In this embodiment, the connection between pin 3 of the power tube Q1 and the inductor L1 is connected to pin 2 of the diode D1, pin 1 of the diode D1 is connected to the ground terminal GND, the left end of the capacitor C1 is connected to the ground terminal GND, pin 2 of the power tube Q1 is connected to a 24V power supply, the lower end of the current detection resistor R1 is connected to the ground terminal GND, the lower end of the multi-stage amplifier is connected to a variable resistor VR, the resistance of the variable resistor VR is 10K, the left end of the variable resistor VR is connected to VCC5, and the right end of the variable resistor VR is connected to the ground terminal GND.

[0033] Example 2

[0034] See also Figure 2-Figure 6 , a LED constant current drive controller with wide load response, Figure 3In the PWM control chip, two error amplifiers, a sawtooth oscillator, a PWM generator, an output control circuit, etc. are integrated. In this application, one of the two error amplifiers is applied to voltage and the other is applied to current. For the convenience of description, they are called voltage error amplifier and current error amplifier respectively. The positive input of the error amplifier is the 1st and 16th pins of the chip, and the negative input is the 2nd and 15th pins of the chip. When the voltage of the positive input pin is higher than the negative input pin, the output voltage of the error amplifier rises. The outputs of the two error amplifiers are connected. When the output of any of the two error amplifiers increases, their superimposed output also increases. Then, the superimposed output is sent to the PWM generator together with the output of the sawtooth oscillator. The PWM control chip has 2 PWM signal outputs, which are combined into one in this application. The specific circuit working principle is as follows (the product has a total of 8 load output channels, and one of the channels is now described):

[0035] When the load is connected, Figure 4 The load detection circuit in the Figure 5 The CPU changes the state of the address lines ADDR0~ADDR2 to make the channel select IC output the 13th signal to the 3rd pin and enter the CPU. After comparing this signal with its internal data one by one, the CPU can determine the model of the connected load. Then, the CPU sends the SPI control line of the 9th~11th pin to the Figure 6 The output of the digital potentiometer is connected to the Figure 6 At R26 of the digital potentiometer, the output of the digital potentiometer determines the gain of amplifier 2. So far, the gain of amplifier 2 has been determined. Figure 6 The VR4 potentiometer is used to compensate the error of the digital potentiometer.

[0036] Then, the CPU sets the output capacitor C1 of pin 26 to a high level (capacitor C1 is low level when there is no load). Capacitor C1 is divided into three paths, one of which is sent to Figure 3 The PWM chip starts to output PWM signal. The PWM signal is then input to Figure 4 The positive electrode of ZD3. ZD3, D9, R39, and Q7 form a driving circuit to drive the power tube Q1 to work. After the power tube Q1 works, Figure 4 Point A in the circuit will get the output voltage.

[0037] The other side of capacitor C1 is connected to Figure 4The positive electrode of ZD4. ZD4, D8, Q8, and R17 form a driving circuit to drive the power tube Q2 to keep saturated and turned on. After the power tube Q2 is turned on, the output voltage supplies power to the load, and the load current flows through the current detection resistor R1, and a voltage is obtained at point B. Figure 6 In the circuit, potentiometer VR3, R36 and R31 divide the 5V voltage to obtain a small voltage, which is superimposed with the voltage at point B and sent to the first-stage amplifier. Two-stage amplifier, three-stage magnification adjustment. The dynamic response of the amplifier is greatly improved, and the response curve is also closer to linear.

[0038] Figure 3 In the circuit, the third path of capacitor C1 is divided by R57 and R24 and then sent to pin 2 of the PWM control chip as the reference voltage for overvoltage protection. Figure 4 The output voltage at point A is added to Figure 3 At R10 in the middle, after being divided by R10 and R19, it is added to pin 1 of the PWM control chip. When the output voltage is too high, the voltage of pin 1 will be higher than that of pin 2. The voltage error amplifier inside the chip will control the PWM duty cycle of the chip output to decrease, causing the output voltage at point A to decrease. If the voltage of pin 1 is lower than that of pin 2, the PWM duty cycle of the chip output will be determined by the current error amplifier. The current error amplifier is used to detect the output current and use the output current to adjust the size of the PWM duty cycle.

[0039] Figure 6 The final output voltage of the amplifier can reach up to 2.5V. This output is connected to Figure 3 The current detection input point of the PWM control chip, that is, pin 16 of the chip. Figure 3 The medium brightness adjustment signal comes from Figure 6 CH1. Figure 6 In the figure, K4 is a selection switch, and the brightness adjustment signal CH1 can come from the brightness adjustment knob RP1 on the product panel, or select another output value of the digital potentiometer. The variation range of the brightness adjustment signal is 0~5V. After current limiting and voltage division by R54 and R21, a control signal with a variation range of 0~2.5V is obtained. This signal is loaded to pin 15 of the PWM control chip and compared with pin 16 to control the output PWM duty cycle. Here, in the conventional LED control chip circuit, this voltage is directly taken from the current detection resistor RCS ( Figure 1 ), in order not to affect the current path of the load and reduce heat generation, RCS is usually very small, about 0.05 ~ 0.2Ω. Assuming the load current is 1A, RCS is 0.1Ω, then the maximum voltage is only 0.1V. Therefore, compared with conventional LED control circuits, this control range is very wide.

[0040] The circuit constant current control process is: when the load current decreases → Figure 4 The voltage at point B decreases → Figure 6 The voltage at the current detection input point drops → Figure 6 The voltage at the output point of the amplifier drops → Figure 3 The voltage of the chip pin 16 is lower than that of the pin 15 → the PWM duty cycle increases → Figure 4 The conduction time of power tube Q1 increases → Figure 4 The output voltage at point A increases → the load current increases. If the load current increases, the above process is reversed, and the voltages of pins 16 and 15 of the PWM control chip eventually reach a dynamic balance. The load current at this time is the current corresponding to the LED load brightness expected by the user.

[0041] When the user disconnects the load, the CPU will Figure 4 The load detection circuit gets the signal change and then controls the capacitor C1 to become 0V. At the same time, Figure 3 Pin 2 of the PWM chip also becomes 0V. Figure 4 Inductor L1 and capacitor C2 exist in the circuit, and the output voltage at point A will not immediately become 0V. The PWM signal is quickly turned off. Figure 4 There is no PWM signal input to ZD3, the drive circuit does not work, and the power tube Q1 turns off the output. Figure 4 The input of the driving circuit of the medium power tube Q2 is also 0V, and the power tube Q2 also turns off the output.

[0042] In summary, this control circuit has the functions of constant current control and voltage overvoltage protection, so as to protect the load. At the same time, the parameters of the amplifier can be adjusted according to the load model, so that the current regulation is more accurate and the load current is more stable.

[0043] In summary, when in use, the PWM control chip generates a PWM signal output to the drive circuit 1 by detecting the input of the multi-stage amplifier and the voltage detection circuit, and controls the conduction and cutoff of the power tube Q1. The 24V power supply enters from the 2nd foot of Q1 and outputs from the 3rd foot. After being filtered by the inductor L1 and the capacitor C1, it becomes a smooth DC output to point A;

[0044] The load detection circuit will continuously detect whether there is a load connected to the load interface and the type of load at a certain interval. Different types of loads will generate different signals and output them to the CPU.

[0045] If a load is connected, the CPU will output instructions to the digital potentiometer according to the model of the connected load to control the maximum amplification factor of the multi-stage amplifier, thereby controlling the maximum current of this model of load;

[0046] At the same time, the CPU outputs a signal to the drive circuit 2 to turn on the power tube Q2. The output voltage passes through Q2 and enters from the 1st pin of the load interface to supply power to the load. It is output from the 3rd pin of the load interface and returns to the negative pole of the power supply through the current detection resistor R1. The load is powered on and starts working.

[0047] The change of current will cause the voltage of point B on R1 to change. The multi-stage amplifier detects the voltage of point B, brightness adjustment and the input of the digital potentiometer, amplifies it and sends it to the PWM control chip to form a closed-loop control of the current.

[0048] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A LED constant current drive controller with wide load response, characterized in that: It includes a PWM control chip, a drive circuit 1, a power tube Q1, an inductor L1, a capacitor C1, a voltage detection circuit, a power tube Q2, a drive circuit 2, a load interface, a load detection circuit, a CPU, a digital positioner, a multi-stage amplifier, and a current detection resistor R1. The PWM control chip is electrically connected to the left end of the drive circuit 1; The driving circuit 1 is electrically connected to the pin No. 1 of the power tube Q1, the pin No. 3 of the power tube Q1 is electrically connected to the inductor L1, the lower end of the inductor L1 is electrically connected to the capacitor C1, and the inductor L1 is connected to the lower end of the voltage detection circuit; The voltage detection circuit is electrically connected to pin No. 2 of the power tube Q2, pin No. 1 of the power tube Q2 is connected to the drive circuit 2, the drive circuit 2 is connected to the right end of the CPU, the voltage detection circuit is electrically connected to the right end of the PWM control chip, pin No. 3 of the power tube Q2 is electrically connected to pin No. 1 of the load interface, pin No. 2 of the load interface is electrically connected to the load detection circuit, the load detection circuit is connected to the CPU, pin No. 3 of the load interface is electrically connected to the current detection resistor R1, the current detection resistor R1 is electrically connected to a multi-stage amplifier, the multi-stage amplifier is electrically connected to the lower end of the digital position indicator, and the upper end of the digital position indicator is electrically connected to the CPU.

2. The LED constant current drive controller with wide load response according to claim 1, characterized in that: The connection point between the pin 3 of the power tube Q1 and the inductor L1 is connected to the pin 2 of the diode D1 , and the pin 1 of the diode D1 is connected to the ground terminal GND.

3. The LED constant current drive controller with wide load response according to claim 1, characterized in that: The left end of the capacitor C1 is connected to the ground terminal GND.

4. The LED constant current drive controller with wide load response according to claim 1, characterized in that: Pin 2 of the power tube Q1 is connected to a 24V power supply.

5. The LED constant current drive controller with wide load response according to claim 1, characterized in that: The lower end of the current detection resistor R1 is connected to the ground terminal GND.

6. The LED constant current drive controller with wide load response according to claim 1, characterized in that: The lower end of the multi-stage amplifier is connected with a variable resistor VR, and the resistance of the variable resistor VR is 10K.

7. The LED constant current drive controller with wide load response according to claim 6, characterized in that: The left end of the variable resistor VR is connected to VCC5, and the right end of the variable resistor VR is connected to the ground terminal GND.

Images