A LED constant current drive circuit

Abstract

The present invention relates to the field of LED driving technology, and specifically discloses an LED constant current driving circuit, which includes: an input rectifying and filtering unit, a driving unit, a switch control unit and an output unit, wherein the input rectifying and filtering unit is connected to the driving unit, the switch control unit is connected to the driving unit, the output unit is connected to the switch control unit, and the output unit is used to connect at least one group of LED light strings; the input rectifying and filtering unit is used to connect an AC input voltage, and can rectify and filter the AC input voltage; the driving unit can generate a switch driving signal, and the switch driving signal can drive the average value of the charging current of the switch control unit to be equal to the output current of the output unit; the switch control unit can drive the LED lamp beads connected to the output unit to turn on and off according to the switch driving signal. The LED constant current driving circuit provided by the present invention can effectively solve the problem of power frequency flickering of LED driving, and has a simple structure and low cost.

Description

Technical Field

[0001] The present invention relates to the technical field of LED driving, and in particular to an LED constant current driving circuit. Background Art

[0002] In the current LED drivers, all are linear LED drivers. When the input voltage is low, due to the limitation of the charging current capacity of the MOS tube and the reduction of the conduction time, the average current of the output LED will inevitably decrease. If the rated current output of the LED is still to be maintained, power frequency flicker will inevitably occur.

[0003] Therefore, how to solve the power frequency flicker of LED has become a technical problem that needs to be solved urgently by those skilled in the art. Summary of the invention

[0004] The invention provides an LED constant current driving circuit, which solves the problem of LED power frequency flickering that cannot be solved in the related art.

[0005] As one aspect of the present invention, there is provided an LED constant current drive circuit, comprising: an input rectifying and filtering unit, a driving unit, a switch control unit and an output unit, wherein the input rectifying and filtering unit is connected to the driving unit, the switch control unit is connected to the driving unit, the output unit is connected to the switch control unit, and the output unit is used to connect at least one group of LED light strings;

[0006] The input rectifying and filtering unit is used to connect to an AC input voltage and is capable of rectifying and filtering the AC input voltage;

[0007] The driving unit is capable of generating a switch driving signal, and the switch driving signal is capable of driving the average value of the charging current of the switch control unit to be equal to the output current of the output unit;

[0008] The switch control unit can drive the LED lamp bead connected to the output unit to turn on and off according to the switch drive signal.

[0009] Furthermore, the output unit includes two groups of output circuits, and each group of output circuits is connected to a group of LED light strings.

[0010] Furthermore, the switch control unit includes a three-stage MOS tube, wherein two-stage MOS tubes are respectively connected to a group of LED light strings, and each stage MOS tube is connected to an electrolytic capacitor, and the electrolytic capacitor is used to adjust the brightness difference between the two groups of LED light strings.

[0011] Furthermore, a resistor is connected in series to the source of each stage of the MOS tube, and the resistor is used to limit the peak value of the connected MOS tube.

[0012] Furthermore, different LED light string powers correspond to different numbers of MOS tubes.

[0013] Furthermore, the model of the MOS tube is LA2N60.

[0014] Furthermore, each group of the output circuits includes an output control chip, and the model of the output control chip is L1002A.

[0015] Furthermore, the driving unit includes a driving chip.

[0016] Furthermore, the model of the driver chip is L1051.

[0017] The LED constant current driving circuit provided by the present invention has a driving unit capable of generating a switch driving signal, improving the function of the loop to supplement the COMP voltage, and the COMP voltage will increase when the input voltage is relatively low. Therefore, when the COMP voltage increases to a certain level, it is used as a control amount to reduce the reference, thereby reducing the LED output current, so that the average value of the charging current of the switch control unit is equal to the LED output current, thereby achieving the output of the LED without flickering even at low input voltage. Therefore, the LED constant current driving circuit provided by the present invention can effectively solve the problem of power frequency flickering of LED driving, and has a simple structure and low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the present invention but do not constitute a limitation of the present invention. In the accompanying drawings:

[0019] Figure 1 This is a structural block diagram of the LED constant current drive circuit provided by the present invention.

[0020] Figure 2 This is a circuit schematic diagram of the LED constant current drive circuit provided by the present invention.

[0021] Figure 3 This is a circuit schematic diagram of the driver chip provided by the present invention.

[0022] Figure 4 This is a graph of PF value and stroboscopic depth test data using the L1051 driver chip provided by the present invention.

[0023] Figure 5 This is a physical structure diagram of a constant current drive circuit provided by the present invention. DETAILED DESCRIPTION

[0024] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0025] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiment of the present invention. Obviously, the described embodiment is only a part of the embodiment of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work should fall within the scope of protection of the present invention.

[0026] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so as to describe the embodiments of the present invention described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0027] In this embodiment, a LED constant current driving circuit is provided. Figure 1 is a structural block diagram of an LED constant current driving circuit provided according to an embodiment of the present invention. Figure 1 As shown, it includes: an input rectifying and filtering unit 100, a driving unit 200, a switch control unit 300 and an output unit 400, wherein the input rectifying and filtering unit 100 is connected to the driving unit 200, the switch control unit 300 is connected to the driving unit 400, the output unit 400 is connected to the switch control unit 300, and the output unit 400 is used to connect at least one group of LED light strings;

[0028] The input rectifying and filtering unit 100 is used to connect an AC input voltage and can rectify and filter the AC input voltage;

[0029] The driving unit 200 can generate a switch driving signal, and the switch driving signal can drive the average value of the charging current of the switch control unit to be equal to the output current of the output unit;

[0030] The switch control unit 300 can drive the LED lamp bead connected to the output unit to turn on and off according to the switch drive signal.

[0031] It should be understood that the LED constant current drive circuit provided by the embodiment of the present invention, the drive unit can generate a switch drive signal, improve the function of the loop to supplement the COMP voltage, and the COMP voltage will increase when the input voltage is relatively low. Therefore, when the COMP voltage increases to a certain level, it is used as a control amount to reduce the reference, thereby reducing the LED output current, so that the average value of the charging current of the switch control unit is equal to the LED output current, thereby achieving the output of the LED without flicker at low input voltage. Therefore, the LED constant current drive circuit provided by the present invention can effectively solve the problem of power frequency flicker of LED drive, and has a simple structure and low cost.

[0032] In the embodiment of the present invention, Figure 2 As shown, the output unit 400 includes two groups of output circuits, and each group of output circuits is connected to a group of LED light strings.

[0033] More specifically, the switch control unit includes a three-stage MOS tube, wherein two-stage MOS tubes are respectively connected to a group of LED light strings, and each stage MOS tube is connected to an electrolytic capacitor, and the electrolytic capacitor is used to adjust the brightness difference between the two groups of LED light strings.

[0034] More specifically, a resistor is connected in series to the source of each stage of the MOS tube, and the resistor is used to limit the peak value of the connected MOS tube.

[0035] It should be understood that different LED light string powers correspond to different numbers of MOS tubes.

[0036] Preferably, the model of the MOS tube is LA2N60.

[0037] Each group of the output circuits includes an output control chip, and the model of the output control chip is L1002A.

[0038] In the embodiment of the present invention, the driving unit 200 includes a driving chip.

[0039] Preferably, the model of the driver chip is L1051, and the specific structural principle diagram is as follows: Figure 3 shown.

[0040] It should be noted that L1051 is a linear constant current driver chip with high power factor, low harmonic current, low flicker depth and balanced LED brightness, suitable for high-power LED lighting product applications. L1051 drives external MOSFET to control the LED to draw sinusoidal current from the mains, so that the drive system based on L1051 has a higher power factor and lower harmonic current. The 2+1 circuit composed of 2 segments of LED and 1 segment of capacitor, the electrolytic capacitors C1, C2 and C3 in the circuit are all 120V / 150uf, which effectively reduces the LED light flicker and brightness difference, and is suitable for high-quality lighting occasions.

[0041] like Figure 4 The figure shows the PF value and strobe depth test data using the L1051 driver chip.

[0042] The constant current drive circuit based on L1051 requires two sets of LEDs and three-stage MOS. The rated voltage of each set of LEDs is 90V, and the model of each set of MOS is LA2N60. Resistors R13, R14, and R15 in the circuit are used to limit the peak value of MOS and improve reliability.

[0043] Figure 5 As shown, it is a physical structure diagram of the present invention made by using the above-mentioned constant current drive circuit. In the embodiment of the present invention, two groups of LEDs are used, and the current error between the two groups of LEDs is less than 5%, which is suitable for flat panel lights, tri-proof lights, etc. As needed, the differential mode and common mode surge levels of 1KV / 2KV / 4KV can be met. The power fluctuation within the range of 180-264vac is less than 5%, and the requirements of global standards for power factor / THD / sub-harmonics are met (sinusoidal current, meeting global certification standards). When 220vac input, the maximum power is 100W; when 120vac input, the maximum power is 75W.

[0044] It is to be understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of the present invention, but the present invention is not limited thereto. For those of ordinary skill in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A LED constant current drive circuit, characterized in that: include: An input rectifying and filtering unit, a driving unit, a switch control unit and an output unit, wherein the input rectifying and filtering unit is connected to the driving unit, the switch control unit is connected to the driving unit, the output unit is connected to the switch control unit, and the output unit is used to connect at least one set of LED light strings; The input rectifying and filtering unit is used to connect to an AC input voltage and is capable of rectifying and filtering the AC input voltage; The driving unit is capable of generating a switch driving signal, and the switch driving signal is capable of driving the average value of the charging current of the switch control unit to be equal to the output current of the output unit; The switch control unit can drive the LED lamp bead connected to the output unit to turn on and off according to the switch drive signal; The output unit includes two groups of output circuits, each group of output circuits is connected to a group of LED light strings; The switch control unit includes a three-stage MOS tube, wherein two-stage MOS tubes are respectively connected to a group of LED light strings, and each stage MOS tube is connected to an electrolytic capacitor, and the electrolytic capacitor is used to adjust the brightness difference between the two groups of LED light strings; The source of each MOS tube is connected in series with a resistor, which is used to limit the peak value of the connected MOS tube; Different LED light string powers correspond to different numbers of MOS tubes.

2. The LED constant current driving circuit according to claim 1, characterized in that: The model of the MOS tube is LA2N60.

3. The LED constant current driving circuit according to claim 1, characterized in that: Each group of the output circuits includes an output control chip, and the model of the output control chip is L1002A.

4. The LED constant current driving circuit according to claim 1, characterized in that: The driving unit includes a driving chip.

5. The LED constant current driving circuit according to claim 4, characterized in that: The model of the driver chip is L1051.

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