LED constant current output control circuit
By designing an LED constant current output control circuit including a sampling circuit and a regulation control circuit, the problem that the existing constant current source driving circuit cannot adjust the output current is solved, and the adjustment and adaptability of the output current is achieved, and the cost and resource waste are reduced.
Patent Information
- Application Number
- CN202420890617.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-04-26
- Publication Date
- 2025-03-25
- Estimated Expiration
- 2034-04-26
AI Technical Summary
The existing constant current source driving circuit cannot adjust the output current, resulting in the need to set up multiple different constant current tubes in areas and occasions where the current needs to be changed, resulting in high costs, large space occupied, and waste of resources.
An LED constant current output control circuit including a switching tube, a sampling circuit and a regulation control circuit is designed. The current is detected through the sampling circuit and feedback to the regulation control circuit. The conduction state of the switching tube is controlled by using the comparison circuit and the regulation circuit, thereby realizing the adjustable output current.
The constant current source circuit output current is adjustable, adapting to situations where changing current is required, reducing component number and wiring complexity, reducing costs, and expanding application fields.
Smart Images
Figure CN222674532U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the technical field of power supply, and more specifically to an LED constant current output control circuit. Background Art
[0002] In LED driving applications, using a constant current source driving circuit to drive an LED can allow the LED to work under a stable current and avoid the flicker problem caused by a constant voltage circuit. The constant current source driving circuit of the prior art can usually only provide a single constant current and cannot be adjusted. In many fields and occasions where a variable current is required, multiple different constant current tubes need to be set up to provide a constant current under different requirements for the load. Therefore, a large number of repetitive components and wiring are required, resulting in high costs, large space occupation, waste of resources, and other problems, and its application field is greatly limited. Utility Model Content
[0003] The technical problem to be solved by the utility model is to provide an LED constant current output control circuit to achieve the purpose of adjusting the output current of the constant current source circuit.
[0004] In order to solve the above technical problems, the utility model provides an LED constant current output control circuit, comprising a switch tube, a sampling circuit and a regulating control circuit, wherein the switch tube and a load connected to a power supply are connected in series, and the sampling circuit is connected to the output end of the switch tube to sample the current flowing through the switch tube;
[0005] The regulation control circuit includes a comparison circuit, a first regulation circuit and a second regulation circuit. The comparison circuit includes a first operational amplifier. The input end of the first regulation circuit is connected to the sampling circuit, and the output end thereof is connected to the inverting input end of the first operational amplifier. The input end of the second regulation circuit is connected to an external power supply, and the output end thereof is connected to the non-inverting input end of the first operational amplifier. The output end of the first operational amplifier is connected to the control end of the switch tube to control the conduction state of the switch tube.
[0006] A further technical solution is as follows: the sampling circuit comprises a sampling resistor, one end of the sampling resistor is connected to the output end of the switch tube, and the other end is grounded.
[0007] Its further technical solution is: the first regulating circuit includes a ninth resistor and a tenth resistor, and the ninth resistor and the tenth resistor are connected in series, one end of which is connected to the sampling circuit, and the other end is connected to the inverting input end of the first operational amplifier.
[0008] Its further technical solution is: the second adjustment circuit includes a fifth resistor, a seventh resistor and an adjustable resistor, one end of the fifth resistor is connected to an external power supply, and the other end is connected to one end of the adjustable resistor, the other end of the adjustable resistor is grounded through the seventh resistor, and the sliding end of the adjustable resistor is connected to the non-inverting input end of the first operational amplifier.
[0009] A further technical solution is: the regulation control circuit also includes a first capacitor, and the first capacitor is connected between the output end of the first operational amplifier and one end where the ninth resistor and the tenth resistor are connected.
[0010] A further technical solution is: the comparison circuit also includes a second resistor and a third resistor, one end of the second resistor and the third resistor are respectively connected to a TRIM pin of the first operational amplifier, and the other ends of the second resistor and the third resistor are connected to an external power supply.
[0011] A further technical solution is: the regulation control circuit also includes a fourth resistor, and the fourth resistor is connected between the output end of the first operational amplifier and the control end of the switch tube.
[0012] Its further technical solution is: the switch tube is an N-type MOS tube, the drain of the N-type MOS tube serves as the input end of the switch tube and is connected to the load, the source serves as the output end of the switch tube, and the gate serves as the control end of the switch tube.
[0013] Compared with the prior art, the LED constant current output control circuit of the utility model is provided with a sampling circuit and an adjustment control circuit. The sampling circuit can sample the current flowing through the switch tube to obtain a sampling voltage signal representing the current value. The first adjustment circuit in the adjustment control circuit is connected to the sampling circuit, and the second adjustment circuit is connected to the external power supply. The first operational amplifier compares the voltage signals from the first adjustment circuit and the second adjustment circuit, thereby outputting a control signal for controlling the on-off and conduction state of the switch tube. It can be seen that the LED constant current output control circuit of the utility model can control the conduction state of the switch tube according to the current detected by the sampling circuit, that is, when the load current is too large, the current detected by the sampling circuit increases, and the current The voltage rises and is fed back to the first regulating circuit, thereby increasing the voltage at the inverting input terminal of the first operational amplifier. According to the characteristics of the operational amplifier, the output terminal of the first operational amplifier will reduce the output voltage, thereby reducing the conduction capacity of the switch tube to stabilize the current. On the contrary, when the load current becomes smaller, the output voltage of the comparison circuit increases, and the conduction capacity of the control switch tube is improved. Similarly, when the voltage from the second regulating circuit changes, the output of the first operational amplifier will also change, thereby achieving the purpose of adjusting the conduction capacity of the switch tube to achieve the change of output current. It can adapt to occasions where the current needs to be changed or the current changes, the applicable occasions are greatly expanded, and the cost can be saved, with good economy and practicality. BRIEF DESCRIPTION OF THE DRAWINGS
[0014] Figure 1 The utility model is a circuit block diagram of a specific embodiment of the LED constant current output control circuit.
[0015] Figure 2 It is a circuit diagram of a specific embodiment of the LED constant current output control circuit of the utility model. DETAILED DESCRIPTION
[0016] In order to enable ordinary technicians in the field to more clearly understand the purpose, technical solutions and advantages of the utility model, the utility model is further explained below in conjunction with the accompanying drawings and embodiments.
[0017] Reference Figure 1The LED constant current output control circuit of the utility model includes a switch tube 11, a sampling circuit 12 and a regulating control circuit 13, wherein the switch tube 11 is connected in series with a load RL connected to a power supply VCC, and the sampling circuit 12 is connected to the output end of the switch tube 11 to sample the current flowing through the switch tube 11; the regulating control circuit 13 includes a comparison circuit 133, a first regulating circuit 131 and a second regulating circuit 132, and the comparison circuit 133 includes a first operational amplifier U1, the input end of the first regulating circuit 131 is connected to the sampling circuit 12, and the output end thereof is connected to the inverting input end of the first operational amplifier U1, the input end of the second regulating circuit 132 is connected to an external power supply, and the output end thereof is connected to the non-inverting input end of the first operational amplifier U1, and the output end of the first operational amplifier U1 is connected to the control end of the switch tube 11 to control the conduction state of the switch tube 11. In this embodiment, one end of the load RL is connected to the power supply VCC, and the other end is connected to the input end of the switch tube 11. It can be understood that the power supply VCC is the power supply voltage output after the rectifier circuit in the constant current source drive circuit rectifies the AC input power supply, which can be 12V or 24V, etc. Based on the above design, the LED constant current output control circuit of the present invention can control the conduction state of the switch tube 11 according to the current detected by the sampling circuit 12. When the current input to the load RL is too large, the current detected by the sampling circuit 12 is fed back to the first regulating circuit 131, and the first regulating circuit 131 controls the output of the first operational amplifier U1, that is, the voltage at the inverting input terminal of the first operational amplifier U1 increases. According to the characteristics of the operational amplifier, the output terminal of the first operational amplifier U1 will reduce the output voltage, thereby reducing the conduction ability of the switch tube 11 to stabilize the current. On the contrary, when the current of the load RL becomes smaller, the output voltage of the comparison circuit 133 increases, and the conduction ability of the control switch tube 11 is improved. Similarly, the LED constant current output control circuit of the present invention can also change the output of the first operational amplifier U1 according to the voltage change of the second regulating circuit 132, so as to achieve the purpose of adjusting the conduction ability of the switch tube 11 and realizing the output current change.
[0018] Specifically, refer to Figure 2 In some embodiments, the switch tube 11 is an N-type MOS tube Q1, the drain of the N-type MOS tube Q1 serves as the input end of the switch tube 11, which is connected to the load RL, the source of the MOS tube Q1 serves as the output end of the switch tube 11, which is connected to the input end of the sampling circuit 12, and the gate of the MOS tube Q1 serves as the control end of the switch tube 11, which is connected to the output end of the first operational amplifier U1 in the comparison circuit 133.
[0019] In some embodiments, the sampling circuit 12 includes a sampling resistor R11, one end of which is connected to the output end (i.e., the source) of the switch tube 11, and the other end is grounded to sample the current flowing through the switch tube 11 to obtain a sampling voltage signal representing the current value.
[0020] Continue to refer to Figure 2 In this embodiment, the model of the first operational amplifier U1 is OPA227, the first regulating circuit 131 includes a ninth resistor R9 and a tenth resistor R10, one end of the ninth resistor R9 and the tenth resistor R10 connected in series is connected to the sampling resistor R11 and the source of the switch tube 11, and the other end is connected to the inverting input end (pin 2) of the first operational amplifier U1; and the second regulating circuit 132 includes a fifth resistor R5, a seventh resistor R7 and an adjustable resistor R6, one end of the fifth resistor R5 is connected to an external power supply, and the other end is connected to one end of the adjustable resistor R6, the other end of the adjustable resistor R6 is grounded through the seventh resistor R7, the sliding end of the adjustable resistor R6 is connected to the in-phase input end (pin 3) of the first operational amplifier U1, and the output end (pin 6) of the first operational amplifier U1 is connected to the gate of the switch tube 11. Preferably, in this embodiment, the external power supply can be a 5V power supply. Based on the above design, the ninth resistor R9 and the tenth resistor R10 constitute a negative feedback regulation circuit, and the output voltage of the second regulation circuit 132 can be changed by moving the sliding end of the adjustable resistor R6 in the second regulation circuit 132, thereby changing the output of the first operational amplifier U1 to adjust the conduction capacity of the switch tube 11 to achieve a change in the output current.
[0021] Furthermore, the comparison circuit 133 also includes a second resistor R2 and a third resistor R3, one end of the second resistor R2 and the third resistor R3 are respectively connected to a TRIM pin (pin 1 and pin 8) of the first operational amplifier U1, and the other ends of the second resistor R2 and the third resistor R3 are connected to a 5V power supply. Based on the above design, the second resistor R2 and the third resistor R3 form a zero adjustment circuit with the TRIM pin of the first operational amplifier U1, which can adjust the output offset voltage of the operational amplifier so that the switch tube 11 can be in the off state when the operational amplifier input is minimum (for example, when the input is zero). It can be understood that in some other embodiments, the first operational amplifier U1 can also use other types of operational amplifiers with TRIM pins, for example, an operational amplifier with model OPA228 can be selected.
[0022] In some embodiments, the regulation control circuit 13 also includes a fourth resistor R4 and a first capacitor C1, the fourth resistor R4 is connected between the output end of the first operational amplifier U1 and the gate of the switch tube 11, and the first capacitor C1 is connected between the output end of the first operational amplifier U1 and one end where the ninth resistor R9 and the tenth resistor R10 are connected.
[0023] The LED constant current output control circuit of the utility model cooperates with the sampling circuit 12, the regulating control circuit 13 and the switch tube 11, and controls the switch tube 11 to work in the linear region and control its conduction capacity, thereby adjusting the conduction current size on the load RL. Figure 2 If the current input to the load RL is too large, the voltage at one end of the sampling resistor R11 will increase, causing the voltage at the inverting input end of the first operational amplifier U1 to increase, thereby reducing the voltage output at the output end of the first operational amplifier U1 and reducing the conduction capacity of the switch tube 11 to achieve adjustable output current, and the output current after adjustment is a stable current. Conversely, when the current input to the load RL becomes smaller, the output voltage of the first operational amplifier U1 increases, thereby improving the conduction capacity of the switch tube 11, thereby adjusting the conduction current on the load RL. Similarly, the LED constant current output control circuit of the utility model can also change the output voltage of the second adjustment circuit 132 by moving the sliding end of the adjustable resistor R6 in the second adjustment circuit 132, thereby adjusting the voltage at the inverting input end of the first operational amplifier U1, changing the output of the first operational amplifier U1, and adjusting the conduction capacity of the switch tube 11 to achieve the purpose of output current change.
[0024] In summary, the LED constant current output control circuit of the utility model can adapt to occasions where a variable current or a current change is required, the applicable occasions are greatly expanded, and the cost can be saved, and it has good economy and practicality.
[0025] The above description is only a preferred embodiment of the utility model, and does not limit the utility model in any form. Those skilled in the art can make various equivalent changes and improvements based on the above embodiments, and all equivalent changes or modifications made within the scope of the claims should fall within the protection scope of the utility model.
Claims
1. An LED constant current output control circuit, characterized in that: The LED constant current output control circuit includes a switch tube, a sampling circuit and a regulation control circuit, wherein the switch tube is connected in series with a load connected to a power supply, and the sampling circuit is connected to the output end of the switch tube to sample the current flowing through the switch tube; The regulation control circuit includes a comparison circuit, a first regulation circuit and a second regulation circuit. The comparison circuit includes a first operational amplifier. The input end of the first regulation circuit is connected to the sampling circuit, and the output end thereof is connected to the inverting input end of the first operational amplifier. The input end of the second regulation circuit is connected to an external power supply, and the output end thereof is connected to the non-inverting input end of the first operational amplifier. The output end of the first operational amplifier is connected to the control end of the switch tube to control the conduction state of the switch tube.
2. The LED constant current output control circuit according to claim 1, characterized in that: The sampling circuit comprises a sampling resistor, one end of which is connected to the output end of the switch tube, and the other end of which is grounded.
3. The LED constant current output control circuit according to claim 1 or 2, characterized in that: The first regulating circuit includes a ninth resistor and a tenth resistor, and the ninth resistor and the tenth resistor are connected in series, one end of which is connected to the sampling circuit, and the other end of which is connected to the inverting input end of the first operational amplifier.
4. The LED constant current output control circuit according to claim 3, characterized in that: The second adjustment circuit includes a fifth resistor, a seventh resistor and an adjustable resistor, one end of the fifth resistor is connected to an external power supply, and the other end is connected to one end of the adjustable resistor, the other end of the adjustable resistor is grounded through the seventh resistor, and the sliding end of the adjustable resistor is connected to the non-inverting input end of the first operational amplifier.
5. The LED constant current output control circuit as claimed in claim 3, characterized in that: The regulation control circuit further includes a first capacitor connected between the output end of the first operational amplifier and one end where the ninth resistor and the tenth resistor are connected.
6. The LED constant current output control circuit according to claim 1, characterized in that: The comparison circuit further includes a second resistor and a third resistor, one end of the second resistor and the third resistor are respectively connected to a TRIM pin of the first operational amplifier, and the other ends of the second resistor and the third resistor are both connected to an external power supply.
7. The LED constant current output control circuit according to claim 1, 4, 5 or 6, characterized in that: The regulation control circuit also includes a fourth resistor, which is connected between the output end of the first operational amplifier and the control end of the switch tube.
8. The LED constant current output control circuit according to claim 1, characterized in that: The switch tube is an N-type MOS tube, the drain of which serves as the input end of the switch tube and is connected to the load, the source of which serves as the output end of the switch tube, and the gate of which serves as the control end of the switch tube.