High-precision dimming LED power supply

Abstract

The utility model relates to the technical field of LED power supplies, and discloses a high-precision dimming LED power supply, which aims at solving the technical problem that the dimming precision of the existing LED power supply is poor, and comprises an anti-interference EMC circuit, a rectifying circuit and a power factor correction circuit for adjusting the power factor of direct current, a constant current circuit is arranged at the rear stage of the power factor correction circuit, the constant current circuit comprises a constant current driving module U1 and an NMOS tube Q2, the current sampling end of the constant current driving module U1 is grounded through a sampling resistor R49 and grounded through the sampling resistor R49, the magnitude of output voltage can be changed according to the magnitude of the sampling resistor R49, and the purpose of constant current is achieved; the drain electrode end of the constant-current driving module U1 is connected with the source electrode of the NMOS transistor Q2, the drain electrode of the NMOS transistor Q2 is connected with the positive electrode of the output end of the rectifying circuit sequentially through the magnetic bead L5 and the diode D12, the constant-current circuit can provide stable current output, LED lamp flickering and damage caused by current fluctuation are avoided, and the lighting quality is improved.

Description

Technical Field

[0001] The utility model relates to the technical field of LED power supplies, in particular to a high-precision dimming LED power supply. Background Art

[0002] As a solid-state electric light source, LED has a strong discrete electrical characteristic and plays an important role in lighting, video image display, dimming, fill light and other application fields. However, the stability of LED light emission directly affects the quality of these applications. The traditional driving method may cause LED flicker, which mainly comes from the interference of AC mains power grid and the stability of the subsequent current. The mains power grid is affected by other interferences and there are clutters. If the current is not properly controlled in the DC part, flickering will occur. Although this flicker is not easy to be detected by the human eye, it has a real impact on high-speed photography and the physiological effects of the human eye. Therefore, it is very important to adjust and control the output current, and the existing dimming technology is not good in accuracy. Utility Model Content

[0003] The purpose of the utility model is to provide a high-precision dimming LED power supply to solve the technical problem of poor dimming accuracy of the LED power supply.

[0004] To achieve the above purpose, the specific technical solution of a high-precision dimming LED power supply of the utility model is as follows:

[0005] A high-precision dimming LED power supply, including an EMC circuit for anti-interference, a rectifier circuit for converting commercial AC power into DC power, and a power factor correction circuit for adjusting the power factor of DC power. The power factor correction circuit is provided with a constant current circuit at the rear stage. The constant current circuit includes a constant current drive module U1 and an NMOS tube Q2. The enable end of the constant current drive module U1 is connected to a PWM signal input circuit; the output current closed-loop control compensation end of the constant current drive module U1 is grounded through a capacitor C34, and the current sampling end of the constant current drive module U1 is grounded through a sampling resistor R49; the drain end of the constant current drive module U1 is connected to the NMOS tube Q2. The source of the S tube Q2 is connected, the drain of the NMOS tube Q2 is connected to the positive output terminal of the rectifier circuit through the magnetic bead L5 and the diode D12 in sequence, the drain of the NMOS tube Q2 is used as the negative output terminal of the LED power supply through the inductor L6, the gate of the NMOS tube Q2 is connected to the positive output terminal of the rectifier circuit through the resistor R52, the resistor R51, and the resistor R50 in sequence, and the two ends of the resistor R52 are connected in parallel with a diode D18; the power supply end of the constant current drive module U1 is connected to the positive output terminal of the rectifier circuit through the resistor R51 and the resistor R50 in sequence, and the power supply end is grounded through the capacitor C36; the ground end of the constant current drive module U1 is grounded.

[0006] The enable terminal of the constant current drive module U1 is used to input a PWM signal. The PWM signal controls the enable terminal of U1 to achieve precise control of the output current, thereby adjusting the brightness of the LED. The duty cycle of the PWM signal determines the brightness level of the LED.

[0007] The output current closed-loop control compensation terminal and current sampling terminal of the constant current drive module U1 are used for closed-loop control. The current sampling terminal is grounded through the sampling resistor R49. The constant current drive module U1 adjusts the output current according to the voltage feedback signal on R49. By changing the size of R49, the size of the output current can be accurately controlled to ensure the stability and consistency of the LED under different brightness settings.

[0008] The drain end of the constant current drive module U1 is connected to the source of the NMOS tube Q2. The drain of the NMOS tube Q2 is connected to the positive output terminal of the rectifier circuit through the magnetic bead L5 and the diode D12, and is used as the negative output terminal of the LED power supply through the inductor L6. The gate of the NMOS tube Q2 is connected to the positive output terminal of the rectifier circuit through resistors R52, R51, and R50, and a diode D18 is connected in parallel at both ends of R52. It ensures that Q2 can switch accurately under the control of the PWM signal, thereby stably controlling the current.

[0009] Since the constant current circuit design uses PWM signal control, closed-loop current control and precise sampling feedback, it can achieve high-precision current control and dimming effects. The PWM signal adjusts the LED current by changing the duty cycle, the closed-loop control ensures the current accuracy, and the sampling feedback further accurately outputs the current. These designs ensure linear adjustment and high-precision control of the LED brightness.

[0010] The constant current circuit achieves high-precision dimming effect through a variety of precise control methods, ensuring a wide adjustable brightness range, high dimming accuracy and good light source stability of the LED lamp.

[0011] Furthermore, the PWM signal input circuit includes a PNP-type transistor Q10 and an NPN-type transistor Q11, the base of the transistor Q11 inputs the PWM signal through a resistor R53, the emitter of the transistor Q11 is grounded, the collector of the transistor Q11 is connected to the power supply VCC2 through resistors R54 and R55 in sequence, the base of the transistor Q10 is connected to the intermediate node of the resistor R54 and the resistor R55, the emitter of the transistor Q10 is connected to the power supply VCC2 through a resistor R56, and the collector of the transistor Q10 is connected to the enable end of the constant current drive module U1.

[0012] Furthermore, the power factor correction circuit includes capacitor C2, capacitor C12, diode D14 and diode D15, the positive electrode of capacitor C2 and the positive electrode of diode D15 are connected to the positive electrode of the output end of the rectifier circuit, the negative electrode of capacitor C12 and the cathode of diode D14 are grounded, the negative electrode of capacitor C2 is connected to the cathode of diode D14, and the positive electrode of capacitor C12 is connected to the anode of diode D15. A diode D16 and a resistor R48 are also provided, the cathode of diode D16 is connected to the first end of resistor R48, the anode of diode D16 is connected to the cathode of diode D14, and the second end of resistor R48 is connected to the anode of diode D15.

[0013] The high-precision dimming LED power supply provided by the utility model has the following advantages:

[0014] The electromagnetic interference generated by the power supply is effectively filtered and suppressed by the EMC circuit, ensuring that the power supply works stably in a complex electromagnetic environment, improving the electromagnetic compatibility of the system, reducing interference to other electronic devices, and ensuring the reliability and stability of the system; power factor correction improves efficiency, and the power factor correction circuit adjusts the power factor of the DC power, reduces harmonic pollution of the power grid, improves the utilization rate of electric energy, improves the power factor of the power supply, and reduces reactive power loss; a constant current circuit is set at the rear stage of the power factor correction circuit to ensure the constancy of the output current, improve the service life and stability of the LED lamp, and the constant current circuit can provide a stable current output, avoid flickering and damage of the LED lamp caused by current fluctuations, and improve the lighting quality; the PWM signal accurately controls the dimming, and the enable end of the constant current drive module U1 is connected to the PWM signal input circuit. The circuit can be accurately controlled and adjusted through the PWM signal to achieve a high-precision dimming effect. In summary, the high-precision dimming LED power supply provided by the utility model has the advantages of anti-interference, high power factor, strong stability, and high dimming accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 The structure diagram of the EMC circuit and the rectifier circuit provided by the utility model;

[0016] Figure 2 A structural diagram of a power factor correction circuit provided for the utility model;

[0017] Figure 3 A structural diagram of a constant current circuit provided by the utility model;

[0018] Figure 4 This is a structural diagram of the PWM signal input circuit provided by the utility model. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical solution and advantages of the utility model more clear, the utility model is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the utility model and are not used to limit the utility model.

[0020] See also Figures 1 to 4 The utility model provides a high-precision dimming LED power supply, including an EMC circuit for anti-interference, a rectifier circuit for converting commercial AC power into DC power, and a power factor correction circuit for adjusting the power factor of DC power. The rear stage of the power factor correction circuit is provided with a constant current circuit.

[0021] By setting up the EMC circuit, the electromagnetic interference generated by the power supply can be effectively filtered and suppressed to ensure the stable operation of the power supply in a complex electromagnetic environment. The electromagnetic compatibility of the system can be improved, the interference to other electronic equipment can be reduced, and the reliability and stability of the system can be ensured.

[0022] The power factor correction circuit adjusts the power factor of DC power, reduces harmonic pollution in the power grid, and improves the utilization rate of electric energy. It improves the power factor of the power supply to make it close to 1, reduces reactive power loss, and improves the load capacity of the power grid.

[0023] A constant current circuit is set at the back stage of the power factor correction circuit to ensure the constancy of the output current and improve the service life and stability of the LED lamp. The constant current circuit can provide a stable current output, avoid flickering and damage of the LED lamp caused by current fluctuations, and improve the lighting quality.

[0024] See also Figure 1 The EMC circuit includes an inductor L3 and an inductor L4 connected in series in the live wire L and the neutral wire N, respectively, and a varistor CVR and a capacitor C1 connected between the live wire L and the neutral wire N. The front stage of the inductor L3 is also connected in series with a fuse F1, the varistor CVR is set in the front stage of the inductor L3 and the inductor L4, the capacitor C1 is set in the rear stage of the inductor L3 and the inductor L4, and the two ends of the inductor L3 are also connected in parallel with a resistor R46. The rectifier circuit is composed of a rectifier bridge U2, and the positive electrode of the output end of the rectifier bridge U2 is used as the positive electrode of the power supply to the LED.

[0025] The series configuration of inductors L3 and L4 can effectively suppress conducted electromagnetic interference and reduce the electromagnetic interference of the circuit to the power grid and surrounding equipment.

[0026] The varistor CVR set between the live wire L and the neutral wire N can respond quickly in the case of overvoltage, absorb surge energy, and protect subsequent circuit components from damage by high voltage. The fuse F1 connected in series to the front end of the inductor L3 can also be blown in time when the current is too large to prevent circuit damage or fire risk.

[0027] The parallel configuration of capacitor C1 can effectively filter out high-frequency noise and voltage ripple in the power supply, provide a smoother DC voltage, and help improve the stability of the rectifier circuit and LED lamp.

[0028] The resistor R46 connected in parallel at both ends of the inductor L3 can consume part of the energy stored in the inductor, avoid voltage spikes caused by the inductor at the switching moment, and improve the reliability and stability of the circuit.

[0029] The positive pole of the output end of the rectifier bridge U2 serves as the positive pole of the power supply to the LED, and can efficiently convert AC power into DC power.

[0030] It can be seen that the EMC circuit design not only effectively improves electromagnetic compatibility and reduces electromagnetic interference, but also ensures the safety and stability of the circuit through multiple protection mechanisms, providing a stable and reliable power supply environment for LED lamps.

[0031] See also Figure 2 The circuit is a passive power factor correction circuit, including capacitor C2, capacitor C12, diode D14 and diode D15, the positive electrode of capacitor C2 and the positive electrode of diode D15 are connected to the positive electrode of the output end of the rectifier circuit, the negative electrode of capacitor C12 and the cathode of diode D14 are grounded, the negative electrode of capacitor C2 is connected to the cathode of diode D14, and the positive electrode of capacitor C12 is connected to the anode of diode D15. A diode D16 and a resistor R48 are also provided, the cathode of diode D16 is connected to the first end of resistor R48, the anode of diode D16 is connected to the cathode of diode D14, and the second end of resistor R48 is connected to the anode of diode D15.

[0032] Power factor correction is mainly achieved through capacitor charging and discharging. First, it will pass through capacitor C2, diode D16, resistor R48 and capacitor C12 in sequence and enter the ground to form a loop. Capacitor C2 and capacitor C12 are actually connected in series, so each will get half of the voltage.

[0033] The peak voltage of the rectified AC power is about 310V. Capacitor C2 and capacitor C12 each receive a voltage of 155V. After the rectified power comes in, the waveform is still a sine wave. The voltage will change from the minimum value to the peak value. When it drops from the peak value, capacitor C2 will discharge through the load and diode D14. The discharge speed is higher than the speed of the AC voltage drop. The AC voltage continues to drop, and capacitor C12 and diode D15 will discharge through the load. When the negative half cycle of the AC power comes, due to the presence of diode D16, resistor R48, diode D15 and capacitor C12, two diodes in the rectifier circuit will not be turned on immediately. There will be a short delay. After this short delay, it will enter the power-on state again to charge capacitor C2 and capacitor C12. One of the reasons for the reduction of power factor is the problem of current and voltage phase angle. By adding this power factor correction circuit, the conduction angle of the diode in the rectifier circuit will change, that is, the power factor is improved by changing the phase angle of current and voltage.

[0034] Through the charging and discharging of capacitors C2 and C12 and the action of diodes D14 and D15, the phase angles of current and voltage can be effectively adjusted to make them closer, thereby improving the power factor of the circuit, reducing reactive power, and improving the efficiency of electric energy utilization; since the circuit can improve the current waveform and make it closer to the sine waveform, the generation of high-order harmonics is reduced, which has a positive impact on the stability of the power grid and the normal operation of other electrical equipment; through the charging and discharging process, capacitors C2 and C12 can play a smoothing role when the voltage fluctuates, providing a more stable DC voltage output, which is very important for subsequent circuits, especially LED lights that are sensitive to voltage; the passive power factor correction circuit reduces the reactive component in the current, reduces the power loss in the power transmission process, improves the overall efficiency of electric energy utilization, and reduces the electricity cost; through power factor correction, the power quality is improved, the burden on the power grid is reduced, the life of electrical equipment is extended, and the overall reliability of the system is improved; compared with the active power factor correction circuit, the passive power factor correction circuit has a simple structure, low cost, and no complex control circuits and components, which is easy to design and maintain.

[0035] See also Figure 3The constant current circuit includes a constant current driving module U1 and an NMOS tube Q2. The first end of the constant current driving module U1 is an enable end for inputting a PWM signal; the second end of the constant current driving module U1 is an output current closed-loop control compensation end; the third end of the constant current driving module U1 is a current sampling end, which is grounded through a sampling resistor R49, and can change the size of the output voltage according to the size of the sampling resistor R49 to achieve the purpose of constant current; the fifth end of the constant current driving module U1 is a drain end, which is connected to the source of the NMOS tube Q2, and the drain of the NMOS tube Q2 is connected to the positive output end of the rectifier circuit through a magnetic bead L5 and a diode D12 in turn, and the cathode of the diode is connected to the rectifier The output terminal of the circuit is positive, and the drain of the NMOS tube Q2 is used as the output terminal negative electrode of the LED power supply through the inductor L6. The gate of the NMOS tube Q2 is connected to the output terminal positive electrode of the rectifier circuit through the resistor R52, the resistor R51, and the resistor R50 in turn. A diode D18 is connected in parallel at both ends of the resistor R52, and the anode of the diode D18 is connected to the gate of the NMOS tube Q2; the 6th terminal of the constant current drive module U1 is the power supply terminal, which is connected to the output terminal positive electrode of the rectifier circuit through the resistor R51 and the resistor R50 in turn, and the power supply terminal is grounded through the capacitor C36; the 6th terminal of the constant current drive module U1 is the ground terminal, which is grounded; the 4th and 7th terminals of the constant current drive module U1 are empty pins.

[0036] By inputting a PWM signal through the enable terminal of the constant current drive module U1, accurate control and regulation of the circuit can be achieved; the current closed-loop control compensation terminal and the current sampling terminal of the constant current drive module U1 are connected to the sampling resistor R49, and the output current can be adjusted according to the size of the sampling resistor R49 to achieve constant current output, which helps to protect the LED lamp and extend its service life; the source and drain of the NMOS tube Q2 are connected to the positive output terminal of the rectifier circuit through the inductor L5 and the diode D12, and the inductor and the diode can effectively reduce the current fluctuation and improve the current stability and efficiency; the gate of the NMOS tube Q2 is connected to the positive output terminal of the rectifier circuit through a series of resistors (R52, R51, R50), and the voltage is clamped through the parallel diode D18 to prevent the gate from overvoltage and ensure the safe operation of the NMOS tube; the power supply terminal of the constant current drive module U1 is grounded through a resistor and a capacitor to provide a stable power input to ensure the normal operation of the drive module; through constant current control, the luminous uniformity and brightness stability of the LED lamp are improved, and the brightness change and light attenuation caused by current fluctuation are avoided.

[0037] See also Figure 4The PWM signal input circuit includes a PNP transistor Q10 and an NPN transistor Q11. The base of the transistor Q11 is connected to the PWM signal output end of the single-chip microcomputer controller through a resistor R53, the emitter of the transistor Q11 is grounded, the collector of the transistor Q11 is connected to the power supply VCC2 through resistors R54 and R55 in turn, the base of the transistor Q10 is connected to the middle node of the resistor R54 and the resistor R55, the emitter of the transistor Q10 is connected to the power supply VCC2 through a resistor R56, and the collector of the transistor Q10 is connected to the enable end of the constant current drive module U1.

[0038] R55 and R56 are used to adjust the PWM signal level, which is very useful when the output terminal is accidentally open-circuited. Without the voltage division of the above components, the output voltage may rise, causing damage to the device.

[0039] In practice, the best way to control the brightness of white light LEDs is to modulate the white light LED current through a low-frequency PWM pulse. The low-frequency PWM pulse modulation method can keep the current amplitude of the white light LED constant according to the change of the duty cycle, and can keep the wavelength of the light emitted by the white light LED constant within the entire adjustment range.

[0040] Through the combination of PNP transistor Q10 and NPN transistor Q11, the PWM signal is effectively amplified and converted, ensuring that the PWM signal can reliably drive the constant current drive module U1; the base of the NPN transistor Q11 is connected to the PWM signal output terminal of the single-chip controller through the resistor R53, the emitter is grounded, and the collector is connected to the power supply VCC2 through the resistors R54 and R55. This configuration can ensure the stable transmission of the signal, and the voltage dividing point between the resistors R54 and R55 is connected to the base of the PNP transistor Q10, so that Q10 can accurately respond to the PWM signal; the emitter of the transistor Q10 is connected to the power supply VCC2 through the resistor R56, and the collector is connected to the constant current The enable terminal of the driving module U1 is connected. This design makes it possible that when Q11 is turned on, Q10 is also turned on, and the PWM signal is reliably transmitted to the enable terminal of the constant current driving module U1, thereby realizing the control of the LED brightness; resistors R55 and R56 are used to adjust the PWM signal level. When an accidental open circuit occurs at the output end, appropriate voltage division can prevent the output voltage from being too high, avoid device damage, and enhance the reliability and protection function of the circuit; the low-frequency PWM pulse modulation method controls the brightness of the white light LED, which can make the LED current maintain a constant current amplitude according to the duty cycle, while ensuring that the wavelength of the light wave emitted by the white light LED remains unchanged within the entire adjustment range, maintaining the consistency and stability of the light source.

[0041] It can be seen that the PWM signal input circuit not only realizes stable and reliable PWM signal amplification and conversion, improves the reliability and protection function of the circuit, but also effectively controls the brightness of the white light LED and the consistency of the light wavelength through the low-frequency PWM modulation method.

[0042] In summary, the utility model provides a high-precision dimming LED power supply, which effectively filters and suppresses the electromagnetic interference generated by the power supply through the EMC circuit, ensures that the power supply works stably in a complex electromagnetic environment, improves the electromagnetic compatibility of the system, reduces interference with other electronic devices, and ensures the reliability and stability of the system; power factor correction improves efficiency, the power factor correction circuit adjusts the power factor of the direct current, reduces the harmonic pollution of the power grid, improves the utilization rate of electric energy, improves the power factor of the power supply, and reduces reactive power loss; a constant current circuit is set at the rear stage of the power factor correction circuit to ensure the constancy of the output current, improve the service life and stability of the LED lamp, and the constant current circuit can provide a stable current output, avoid the flickering and damage of the LED lamp caused by current fluctuations, and improve the lighting quality; the PWM signal accurately controls the dimming, and the enable end of the constant current drive module U1 is connected to the PWM signal input circuit. The circuit can be accurately controlled and adjusted through the PWM signal to achieve a high-precision dimming effect. In summary, the high-precision dimming LED power supply provided by the utility model has the advantages of anti-interference, high power factor, strong stability, and high dimming accuracy.

[0043] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A high-precision dimming LED power supply, comprising an EMC circuit for anti-interference, a rectifier circuit for converting commercial AC power into DC power, and a power factor correction circuit for adjusting the power factor of DC power, characterized in that: The rear stage of the power factor correction circuit is provided with a constant current circuit, which includes a constant current drive module U1 and an NMOS tube Q2. The enable end of the constant current drive module U1 is connected to the PWM signal input circuit; the output current closed-loop control compensation end of the constant current drive module U1 is grounded through a capacitor C34, and the current sampling end of the constant current drive module U1 is grounded through a sampling resistor R49; the drain end of the constant current drive module U1 is connected to the source of the NMOS tube Q2, and the drain of the NMOS tube Q2 is connected to the source of the NMOS tube Q2 through a magnetic bead L5, a diode D 12 is connected to the positive output terminal of the rectifier circuit, the drain of the NMOS tube Q2 is used as the negative output terminal of the LED power supply through the inductor L6, the gate of the NMOS tube Q2 is connected to the positive output terminal of the rectifier circuit through the resistor R52, the resistor R51, and the resistor R50 in turn, and the two ends of the resistor R52 are connected in parallel with a diode D18; the power supply end of the constant current drive module U1 is connected to the positive output terminal of the rectifier circuit through the resistor R51 and the resistor R50 in turn, and the power supply end is grounded through the capacitor C36; the ground end of the constant current drive module U1 is grounded.

2. A high-precision dimming LED power supply according to claim 1, characterized in that: The PWM signal input circuit includes a PNP-type transistor Q10 and an NPN-type transistor Q11. The base of the transistor Q11 is connected to the PWM signal through a resistor R53. The emitter of the transistor Q11 is grounded. The collector of the transistor Q11 is connected to the power supply VCC2 through resistors R54 and R55 in sequence. The base of the transistor Q10 is connected to the middle node of the resistor R54 and the resistor R55. The emitter of the transistor Q10 is connected to the power supply VCC2 through a resistor R56. The collector of the transistor Q10 is connected to the enable end of the constant current drive module U1.

3. A high-precision dimming LED power supply according to claim 2, characterized in that: The power factor correction circuit includes a capacitor C2, a capacitor C12, a diode D14 and a diode D15, wherein the positive electrode of the capacitor C2 and the positive electrode of the diode D15 are connected to the positive electrode of the output end of the rectifier circuit, the negative electrode of the capacitor C12 and the cathode of the diode D14 are grounded, the negative electrode of the capacitor C2 is connected to the cathode of the diode D14, and the positive electrode of the capacitor C12 is connected to the anode of the diode D15; a diode D16 and a resistor R48 are also provided, wherein the cathode of the diode D16 is connected to the first end of the resistor R48, the anode of the diode D16 is connected to the cathode of the diode D14, and the second end of the resistor R48 is connected to the anode of the diode D15.

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