A constant-current LED driving circuit capable of step-up and step-down

Abstract

The present invention discloses a constant-current LED driving circuit capable of boosting and bucking, which includes an input circuit, a boost / buck circuit, an output circuit and a control circuit. The boost / buck circuit includes a boost voltage stabilizing circuit and a buck voltage stabilizing circuit. The input circuit is connected to the boost / buck circuit, the boost / buck circuit is connected to the output circuit, the output circuit is connected to the LED lamp, the LED lamp is connected to the control circuit, and the control circuit is connected to the boost / buck circuit. The beneficial effects are as follows: through the intelligent control of the CPU, the constant-current LED driving circuit can work in both the boost state and the buck state, maintaining low loss, low electromagnetic interference and no interference with other electrical equipment when the input voltage and the output voltage are close, improving the electrical efficiency and being beneficial to energy conservation and environmental protection.

Description

Technical Field

[0001] The present invention relates to the technical field of LED driving circuits, and particularly to a constant-current LED driving circuit capable of boosting and bucking voltages. Background Art

[0002] Due to the characteristics of high luminous efficiency, uniform spectral distribution, high energy efficiency, long lifespan, and low-voltage controllability, LED lights are widely used in urban greening lighting, mine lights, flashlights, indoor and outdoor lighting for motor vehicles, etc.

[0003] For existing LED lights, when the input voltage range is relatively large, the output voltage sometimes needs to be boosted and sometimes needs to be bucked. Relatively simple topologies can often only perform single bucking or boosting. Currently, the circuit structures that meet the buck-boost topology are complex, and there are still problems such as unstable output current, low electrical efficiency, and large electromagnetic interference under large-scale voltage fluctuations.

[0004] The above deficiencies need to be improved. Summary of the Invention

[0005] In order to overcome the deficiencies of the existing technology, the present invention provides a constant-current LED driving circuit capable of boosting and bucking voltages.

[0006] The technical solution of the present invention is as follows:

[0007] A constant-current LED driving circuit capable of boosting and bucking voltages includes an input circuit, a boost / buck circuit, an output circuit, and a control circuit. The boost / buck circuit includes a boost voltage regulator circuit and a buck voltage regulator circuit. The input circuit is connected to the boost / buck circuit, the boost / buck circuit is connected to the output circuit, the output circuit is connected to an LED light, the LED light is connected to the control circuit, and the control circuit is connected to the boost / buck circuit.

[0008] According to the present invention of the above solution, it is characterized in that the input circuit includes two input power supplies and a switching circuit, and the switching circuit is used to switch between the two input power supplies.

[0009] According to the present invention of the above solution, it is characterized in that the input circuit includes a relay, a first inductor, and a first capacitor. The second pin of the relay is connected to the first capacitor and the buck voltage regulator circuit respectively through the first inductor.

[0010] According to the present invention of the above solution, it is characterized in that one of the input power supplies is a DC voltage, and the DC voltage is connected to the first pin of the relay through a third diode and a second resistor; one of the input power supplies is a battery, and the battery is connected to the third pin of the relay.

[0011] The present invention according to the above solution is characterized in that the step-down voltage stabilizing circuit includes a second MOS transistor, a first diode and a second inductor. The first pin to the third pin of the second MOS transistor are all connected to the input circuit and one end of an eighth resistor. The fourth pin of the second MOS transistor is respectively connected to the control circuit and the other end of the eighth resistor. The fifth pin to the eighth pin of the second MOS transistor are all connected to one end of the first diode and one end of the second inductor. The other end of the second inductor is connected to the boost voltage stabilizing circuit, and the other end of the first diode is grounded.

[0012] The present invention according to the above solution is characterized in that the boost voltage stabilizing circuit includes a second inductor, a first MOS transistor, a fourth diode and a fourth capacitor. One end of the second inductor is connected to the step-down voltage stabilizing circuit. The other end of the second inductor is respectively connected to the fourth capacitor and the LED lamp through the fourth diode. The other end of the second inductor is respectively connected to a sixth resistor and a seventh resistor through the first MOS transistor and then connected to the control circuit.

[0013] The present invention according to the above solution is characterized in that the control circuit includes a first chip, a triode, a third resistor, a fourth resistor, a fifth resistor and a fifth capacitor. The LED lamp is respectively connected to one end of the third resistor, one end of the fourth resistor and one end of the fifth resistor. The other end of the fifth resistor is respectively connected to the first pin of the first chip and one end of the fifth capacitor. The other ends of the third resistor, the fourth resistor and the fifth capacitor are all grounded;

[0014] The eleventh pin of the first chip is connected to the boost voltage stabilizing circuit. The twelfth pin of the first chip is connected to a 5V voltage. The sixteenth pin of the first chip is respectively connected to a fifteenth resistor and the base of the triode through a sixteenth resistor. The collector of the triode is connected to the step-down voltage stabilizing circuit through a fourteenth resistor. The other end of the fifteenth resistor and the emitter of the triode are grounded.

[0015] The beneficial effect of the present invention according to the above solution is that through the intelligent control of the CPU, the constant-current LED driving circuit can work in both the boost state and the step-down state. When the input voltage and the output voltage are close, the loss is small, the electromagnetic interference brought is low, and it will not interfere with other electrical equipment, which can improve the electrical efficiency and is beneficial to energy conservation and environmental protection. Description of the Drawings

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the accompanying drawings required for use in the embodiments or the description of the prior art. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can be obtained based on these drawings.

[0017] Figure 1 It is a block diagram of the LED drive circuit system of the present invention;

[0018] Figure 2 It is a schematic diagram of the LED drive circuit of the present invention;

[0019] Figure 3 It is a schematic diagram of the input circuit of the present invention;

[0020] Figure 4 It is a schematic diagram of the buck voltage regulation circuit of the present invention;

[0021] Figure 5 It is a schematic diagram of the boost voltage regulation circuit of the present invention;

[0022] Figure 6 It is a schematic diagram of the control circuit of the present invention.

[0023] Each reference numeral in the figure:

[0024] 1. Input circuit, 2. Buck voltage regulation circuit, 3. Boost voltage regulation circuit, 4. Output circuit, 5. Control circuit. Detailed implementation manners

[0025] The following further describes the present invention in conjunction with the accompanying drawings and the implementation manners:

[0026] As Figures 1 to 2 shown, a constant-current LED drive circuit that can boost and buck includes an input circuit 1, a boost / buck circuit, an output circuit 4, and a control circuit 5. The boost / buck circuit includes a buck voltage regulation circuit 2 and a boost voltage regulation circuit 3. The input circuit 1 is connected to the boost / buck circuit, the boost / buck circuit is connected to the output circuit 4, the output circuit 4 is connected to the LED lamp, the LED lamp is connected to the control circuit 5, and the control circuit 5 is connected to the boost / buck circuit.

[0027] As Figure 2 , Figure 3 shown, the input circuit 1 mainly realizes the switching of the input power supply. The input circuit 1 includes an input power supply and a switching circuit. The input power supply of the input circuit 1 includes a DC voltage and a battery BT1, and the DC voltage and the battery BT1 are switched through the switching circuit.

[0028] The DC voltage is a stable DC voltage of 12V flowing through the third diode D3. Boosting is required when powered by the 12V voltage, and bucking is required when powered by the battery BT1.

[0029] The input circuit 1 mainly includes a relay K1, a first inductor L1, and a first capacitor C1. The positive electrode of the third diode D3 is connected to the input voltage, the negative electrode of the third diode D3 is connected to one end of the second resistor R2, and the other end of the second resistor R2 is connected to the first pin 1 of the relay K1. The second pin 2 of the relay K1 is connected to one end of the first inductor L1, the other end of the first inductor L1 is connected to the positive electrode of the first capacitor C1 and the buck-boost voltage stabilizing circuit 2, and the negative electrode of the first capacitor C1 is grounded. The third pin 3 of the relay K1 is connected to one end of the battery BT1, and the other end of the battery BT1 is grounded. The relay is used to switch and select the required input power supply.

[0030] The switching circuit is the relay K1, and the relay K1 is used for switching between the battery BT1 and the input voltage. One end of the relay K1 is connected to the positive electrode of the fifth diode D5, and the negative electrode of the fifth diode is respectively connected to the other end of the relay K1 and the 12V voltage.

[0031] As Figure 2 、 Figure 4 shown, the buck-boost voltage stabilizing circuit 2 mainly realizes bucking the input voltage supplied by the battery to the 18V working voltage required by the LED lamp when the battery supplies power. The buck-boost voltage stabilizing circuit 2 is respectively connected to the input circuit 1, the boost voltage stabilizing circuit 3, and the control circuit 5. Specifically: The buck-boost voltage stabilizing circuit 2 mainly includes a second MOS transistor Q2, a first diode D1, and a second inductor L2. The first pin 1, the second pin 2, and the third pin 3 of the second MOS transistor Q2 are all connected to the other end of the first inductor L1 of the input circuit 1 and one end of the eighth resistor R8. The fourth pin 4 of the second MOS transistor Q2 is respectively connected to the other end of the eighth resistor R8 and the control circuit 5. The fifth pin 5, the sixth pin 6, the seventh pin 7, and the eighth pin 8 of the second MOS transistor Q2 are all connected to the negative electrode of the first diode D1 and one end of the second inductor L2. The positive electrode of the first diode D1 is grounded, and the other end of the second inductor L2 is connected to the boost voltage stabilizing circuit 3.

[0032] As Figure 2 、 Figure 5As shown, the boost voltage regulator circuit 3 mainly boosts the input voltage to the required voltage value of 18V for the operation of the LED lamp when the input voltage is low. The boost voltage regulator circuit 3 is respectively connected to the buck voltage regulator circuit 2 and the control circuit 5. Specifically, the boost voltage regulator circuit 3 mainly includes a second inductor L2, a first MOS transistor Q1, a fourth capacitor C4, and a fourth diode D4. One end of the second inductor L2 is connected to the buck voltage regulator circuit 2, and the other end of the second inductor L2 is respectively connected to the positive electrode of the fourth diode D4 and the drain D of the first MOS transistor Q1.

[0033] The source S of the first field effect Q1 is connected to one end of the sixth resistor R6 and then grounded.

[0034] The gate G of the first MOS transistor Q1 is respectively connected to the other end of the sixth resistor R6 and the eleventh pin 11 of the first chip U1 in the control circuit 5 through the seventh resistor R7.

[0035] The negative electrode of the fourth diode D4 is respectively connected to the positive electrode of the fourth capacitor C4 and the positive electrode of the LED lamp, and the negative electrode of the fourth capacitor C4 is grounded.

[0036] As Figure 2 、 Figure 6 shown, the control circuit 5 is mainly used to boost or buck the power output by detecting the voltage value. The control circuit 5 is respectively connected to the boost voltage regulator circuit 3 and the buck voltage regulator circuit 2. Specifically, the control circuit 5 mainly includes a first chip U1, a triode Q3, a third resistor R3, a fourth resistor R4, a fifth resistor R5, and a fifth capacitor C5. Specifically, the negative electrode of the LED lamp is respectively connected to one end of the third resistor R3, one end of the fourth resistor R4, and one end of the fifth resistor R5. The other end of the fifth resistor R5 is respectively connected to the first pin 1 of the first chip U1 in the control circuit 5 and one end of the fifth capacitor C5. The other ends of the third resistor R3, the fourth resistor R4, and the fifth capacitor C5 are all grounded, and the fifth pin 5 of the first chip U1 is grounded.

[0037] The eleventh pin 11 of the first chip U1 is connected to the boost voltage regulator circuit 3. The twelfth pin 12 of the first chip U1 is connected to a 5V voltage. The sixteenth pin 16 of the first chip U1 is connected to one end of the sixteenth resistor R16. The other end of the sixteenth resistor R16 is respectively connected to one end of the fifteenth resistor R15 and the base of the triode Q3. The collector of the triode Q3 is connected to one end of the fourteenth resistor R14. The other end of the fourteenth resistor R14 is connected to the buck voltage regulator circuit 2. The other end of the fifteenth resistor 15 and the emitter of the triode Q3 are grounded.

[0038] In a constant-current LED driving circuit capable of step-up and step-down, the voltage enters through the third diode D3 and the second resistor R2. The function of the third diode D3 is to prevent the reverse flow of the current of the battery BT1, and the second resistor R2 plays a role of insurance. The relay K1 is used for switching between the battery BT1 and the input voltage. The first inductor L1 and the first capacitor C1 have the functions of filtering and energy storage. The second MOS transistor Q2, the first diode D1 and the second inductor L2 form a step-down voltage stabilizing circuit 2 to complete the function of reducing the voltage. The triode Q3 is used to control the turning on or off of the second MOS transistor Q2. The second inductor L2, the first MOS transistor Q1, the fourth diode D4 and the fourth capacitor C4 form a step-up voltage stabilizing circuit 3 to complete the function of increasing the voltage. The control circuit 5 uses a CPU chip to sample the magnitude of the LED current through the third resistor R3 and the fourth resistor R4, and through software operation, controls the output pulse width waveform to adjust the conduction time and frequency of the first MOS transistor Q1 or the second MOS transistor Q2, so as to achieve the function of constant current.

[0039] The working principle of the present invention:

[0040] When the circuit is working, the current flowing through the LED lamp is detected by the sampling resistor to see if it meets the requirements. If it is not the required predetermined value, then the step-up or step-down of the LED driving circuit is controlled through the control circuit 5 to make its output a constant current. There are the following three situations:

[0041] (1) When the input voltage value is 12V for power supply, the control circuit 5 turns on the step-up voltage stabilizing circuit 3, the control circuit 5 controls the first MOS transistor Q1 to conduct, and the control circuit 5 controls the first MOS transistor Q1 to work in a closed-loop mode, and controls the output current to be constant at the predetermined value.

[0042] (2) When the input voltage is battery-powered, when the supply voltage is in the range of 18V - 21V, the control circuit 5 directly supplies power to the LED lamp and limits the current through the resistor.

[0043] (3) When the input voltage is battery-powered, when the supply voltage is greater than 21V, the control circuit 5 turns off the step-up voltage stabilizing circuit 3, turns on the step-down voltage stabilizing circuit 2, and controls the output current to be constant at the predetermined value.

[0044] Through the intelligent control of the CPU, the constant-current LED driving circuit enables the LED driving circuit to work both in the step-up state and in the step-down state. When the input voltage and the output voltage are close, the loss is small, the electromagnetic interference generated is low, and it does not interfere with other electrical equipment. It can improve the electrical efficiency and is beneficial to energy conservation and environmental protection. The output current of the present invention can be controlled by the control circuit 5 and is suitable for various application requirements. The design of the constant-current LED driving circuit is simple and reliable, which is beneficial to improving the production efficiency.

[0045] It should be understood that those of ordinary skill in the art can make improvements or modifications based on the above description, and all such improvements and modifications shall fall within the protection scope of the appended claims of the present invention.

[0046] The above has given an exemplary description of the present invention patent in conjunction with the accompanying drawings. Obviously, the implementation of the present invention patent is not limited by the above-mentioned manner. As long as various improvements are made by adopting the method concept and technical solution of the present invention patent, or the concept and technical solution of the present invention patent are directly applied to other occasions without improvement, they are all within the protection scope of the present invention.

Claims

1. A constant current LED driving circuit capable of boosting and bucking, characterized in that, It includes an input circuit, a boost / buck circuit, an output circuit and a control circuit. The boost / buck circuit includes a boost voltage regulator circuit and a buck voltage regulator circuit. The input circuit is connected to the boost / buck circuit, the boost / buck circuit is connected to the output circuit, the output circuit is connected to an LED lamp, the LED lamp is connected to the control circuit, and the control circuit is connected to the boost / buck circuit; The boost voltage regulator circuit includes a second inductor, a first MOS transistor, a fourth diode and a fourth capacitor. One end of the second inductor is connected to the buck voltage regulator circuit, and the other end of the second inductor is respectively connected to the fourth capacitor and the LED lamp through the fourth diode. The other end of the second inductor is respectively connected to a sixth resistor and a seventh resistor through the first MOS transistor and then connected to the control circuit; The buck voltage regulator circuit includes a second MOS transistor, a first diode and a second inductor. The first pin to the third pin of the second MOS transistor are all connected to the input circuit and one end of an eighth resistor. The fourth pin of the second MOS transistor is respectively connected to the control circuit and the other end of the eighth resistor. The fifth pin to the eighth pin of the second MOS transistor are all connected to one end of the first diode and one end of the second inductor. The other end of the second inductor is connected to the boost voltage regulator circuit, and the other end of the first diode is grounded; When the circuit works, a sampling resistor is used to detect whether the current flowing through the LED lamp meets the requirements. If it is not the required predetermined value, the boost or buck of the LED drive circuit is controlled through the control circuit to make its output current constant; When the input voltage value is 12V for power supply, the control circuit turns on the boost voltage regulator circuit, controls the first MOS transistor to conduct, controls the first MOS transistor to work in a closed-loop mode, and controls the output current to be constant at a predetermined value; When the input voltage is battery-powered and the supply voltage is in the range of 18V - 21V, the control circuit directly supplies power to the LED lamp and limits the current through a resistor; When the input voltage is battery-powered and the supply voltage is greater than 21V, the control circuit turns off the boost voltage regulator circuit, turns on the buck voltage regulator circuit, and controls the output current to be constant at a predetermined value.

2. The constant-current LED driving circuit capable of boosting and bucking according to claim 1, wherein, The input circuit includes two input power supplies and a switching circuit, and the switching circuit is used to switch between the two input power supplies.

3. The constant-current LED driving circuit capable of boosting and bucking according to claim 2, characterized in that, The input circuit includes a relay, a first inductor and a first capacitor. The second pin of the relay is respectively connected to the first capacitor and the buck voltage regulator circuit through the first inductor.

4. The constant current LED driving circuit capable of boosting and bucking according to claim 3, wherein One of the input power supplies is a DC voltage, and the DC voltage is connected to the first pin of the relay through a third diode and a second resistor; one of the input power supplies is a battery, and the battery is connected to the third pin of the relay.

5. The constant current LED driving circuit capable of step-up and step-down voltage according to claim 1, characterized in that, The control circuit includes a first chip, a triode, a third resistor, a fourth resistor, a fifth resistor, and a fifth capacitor. The LED lamp is respectively connected to one end of the third resistor, one end of the fourth resistor, and one end of the fifth resistor. The other end of the fifth resistor is respectively connected to the first pin of the first chip and one end of the fifth capacitor. The other ends of the third resistor, the fourth resistor, and the fifth capacitor are all grounded; The eleventh pin of the first chip is connected to the boost voltage stabilizing circuit. The twelfth pin of the first chip is connected to a 5V voltage. The sixteenth pin of the first chip is respectively connected to a fifteenth resistor and the base of the triode through a sixteenth resistor. The collector of the triode is connected to the buck voltage stabilizing circuit through a fourteenth resistor. The other end of the fifteenth resistor and the emitter of the triode are grounded.

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