LED high-efficiency constant-current driving circuit

Abstract

The LED high-efficiency constant-current driving circuit comprises an input filtering module and a driving module, the input filtering module comprises a diode, an inductor L1, an inductor L2, a capacitor C1 and a capacitor C2, a voltage input end is electrically connected with an input end of the inductor L2, and an output end of the inductor L2 is electrically connected with anodes of a diode D2 and a diode D3 respectively. The cathode of the diode D2 is electrically connected with one end of the capacitor C1 and the anode of the diode D1, the cathode of the diode D1 is electrically connected with the anode of the diode D4 and one end of the capacitor C2, and the cathode of the diode D4 is electrically connected with the input end of the inductor L1; the driving module comprises an oscillator OSC, a latch, a PWM generator, a comparator, a voltage stabilizer and a driver. The driving module controls the duty ratio of an internal switch to adjust the output current.

Description

Technical Field

[0001] The utility model relates to the field of circuits, in particular to a high-efficiency constant-current driving circuit for LEDs. Background Art

[0002] Early LED driver solutions often performed poorly in terms of power conversion efficiency, meaning more electrical energy was converted into heat rather than light, leading to overall system inefficiency and unnecessary energy waste. Especially in portable devices and large-scale lighting systems, low efficiency not only increases energy consumption but also shortens battery life or increases operating costs. The luminous efficiency and color consistency of LEDs depend largely on the consistency of the current flowing through them. Traditional driver methods struggle to precisely control the LED current in the face of grid voltage fluctuations and load variations, thus affecting lighting quality and LED lifespan. Furthermore, early driver circuits lacked effective overcurrent and short-circuit protection mechanisms, making LEDs susceptible to damage under abnormal conditions, increasing maintenance costs and reducing system reliability. As LED applications expand, from home lighting to outdoor displays to automotive lighting, the demands on driver circuits have become increasingly diverse. Traditional fixed designs often fail to adapt well to the diverse LED load characteristics and system requirements, limiting the widespread adoption of LED technology. Based on the foregoing, the technical solution proposed in this application aims to address these issues. By employing advanced PWM modulation technology, precise closed-loop feedback control, and enhanced protection measures, a high-efficiency and high-stability LED driver solution is achieved. Utility Model Content

[0003] To achieve the above objectives, the present invention provides the following technical solutions:

[0004] A high-efficiency constant-current LED drive circuit includes an input filter module and a drive module. The input filter module includes diodes D1-D4 and inductors L1, L2, capacitors C1, and C2. The voltage input end is electrically connected to the input end of inductor L2. The output end of inductor L2 is electrically connected to the anodes of diodes D2 and D3, respectively. The cathode of diode D2 is electrically connected to one end of capacitor C1 and the anode of diode D1, respectively. The cathode of diode D1 is electrically connected to the anode of diode D4 and one end of capacitor C2, respectively. The cathode of diode D4 is electrically connected to the input end of inductor L1. The input filter module is used to convert AC voltage into a smooth DC voltage. The drive module includes an oscillator OSC, a latch, a PWM generator, a comparator, a voltage regulator, and a driver. The drive module is used to control the duty cycle of internal switches to adjust the output current and maintain a constant LED current. The LED load array is connected to the output end of the drive module.

[0005] Furthermore, the output end of the inductor L1 is electrically connected to the other end of the capacitor C1 and the collector of a transistor Q1, the base of the transistor Q1 is electrically connected to the GATE pin of the driving module, and the cathode of the diode D3 is electrically connected to the resistor R2 and the emitter of the transistor Q1.

[0006] Furthermore, the resistor R2 is electrically connected to the resistor R5, the resistor R5 is electrically connected to the CS2 pin of the driving module, and the resistor R5 is also electrically connected to a resistor R6, which is grounded.

[0007] Furthermore, one end of the capacitor C2 and the resistor R1 is electrically connected to a resistor R3, the other end of the resistor R3 is electrically connected to the CS1 pin of the driving module and a resistor R4, the resistor R4 is electrically connected to the capacitor C3, and the capacitor C3 is electrically connected to the VDD pin of the driving module.

[0008] Furthermore, the driving module includes an oscillator OSC, a latch, a PWM generator, a comparator, a voltage regulator, and a driver. One end of the oscillator OSC is electrically connected to the RT pin, the other end of the oscillator OSC is connected to the S end of the latch, the R end of the latch is electrically connected to the driver, and the two ends of the output buffer driver are respectively electrically connected to the comparators, one of the comparators is electrically connected to the CS1 pin, and the other comparator is electrically connected to the CS2 pin. The O end of the latch is electrically connected to the PWM generator.

[0009] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0010] In this application, the AC voltage first passes through inductor L2 and is then converted into a pulsating DC voltage via a full-bridge rectifier (D1-D4). Next, the filtering stage consisting of L1, C1, and C2 further smoothes the pulsating voltage, providing a relatively clean DC input to the driver module. Resistors R1, R2, R3, R4, R5, and R6, along with capacitors C2 and C3, form the feedback network. The voltage divided by R1 and R3 is fed to the driver module's CS1 pin as primary current feedback. The network of R2, R5, and R6 is used for overcurrent protection or auxiliary current regulation and is connected to the CS2 pin. These feedback signals are used to dynamically adjust the PWM duty cycle within the driver module to maintain a constant LED current. The oscillator OSC sets the circuit's operating frequency, and its signal is processed by a latch and fed to the PWM generator. The latch's state is controlled by an external setting (such as the RT pin) and a feedback signal. A comparator compares the voltages on the CS1 and CS2 pins with an internal reference to achieve precise adjustment of the PWM duty cycle. The PWM signal controls the switch (directly controlling a MOSFET or IGBT through the driver), thereby regulating the average current flowing into the LED. Transistor Q1 acts as a current sensing or short-circuit protection element, working in conjunction with R2. If the output current exceeds the limit, Q1's state changes, affecting the signal at the GATE pin and thus adjusting the driver's output. Capacitor C3 provides decoupling and stabilization at the VDD pin, ensuring a clean power supply to the driver module.

[0011] This application significantly improves power conversion efficiency and reduces power consumption through advanced PWM modulation and precise current control. A precise feedback control mechanism ensures that the LED current is unaffected by power supply voltage fluctuations and load variations, maintaining consistent brightness and extending LED life. Built-in overcurrent protection and short-circuit protection mechanisms increase system reliability and safety. The external resistor network (e.g., RT, R1-R6) can be adjusted to accommodate different LED load requirements, providing flexibility in a variety of applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is the circuit connection diagram of this application; DETAILED DESCRIPTION

[0013] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments 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 efforts are within the scope of protection of the present invention.

[0014] The utility model provides a high-efficiency constant-current LED driving circuit, such as Figure 1As shown, it includes an input filter module and a driver module. The input filter module includes diodes D1-D4 and inductors L1, L2, capacitors C1, and C2. The voltage input end is electrically connected to the input end of inductor L2. The output end of inductor L2 is electrically connected to the anodes of diodes D2 and D3 respectively. The cathode of diode D2 is electrically connected to one end of capacitor C1 and the anode of diode D1 respectively. The cathode of diode D1 is electrically connected to the anode of diode D4 and one end of capacitor C2 respectively. The cathode of diode D4 is electrically connected to the input end of inductor L1. The output end of inductor L1 is electrically connected to the other end of capacitor C1 and the collector of transistor Q1 respectively. The base of transistor Q1 is electrically connected to the GATE pin of the driver module. The cathode of diode D3 is electrically connected to resistor R2 and the emitter of transistor Q1 respectively. Resistor R2 is electrically connected to resistor R5, which is electrically connected to the CS2 pin of the driver module. Resistor R5 is also electrically connected to resistor R6, which is grounded. One end of the capacitor C2 and resistor R1 is also electrically connected to a resistor R3. The other end of resistor R3 is respectively electrically connected to the CS1 pin of the driver module and a resistor R4. Resistor R4 is electrically connected to capacitor C3, and capacitor C3 is electrically connected to the VDD pin of the driver module. The input filter module is used to convert the AC voltage into a smooth DC voltage. The driver module includes an oscillator OSC, a latch, a PWM generator, a comparator, a voltage regulator, and a driver. The driver module is used to control the duty cycle of the internal switch to adjust the output current and maintain a constant LED current. The LED load array is connected to the output end of the driver module. The driver module includes an oscillator OSC, a latch, a PWM generator, a comparator, a voltage regulator, and a driver. One end of the oscillator OSC is electrically connected to the RT pin, the other end of the oscillator OSC is connected to the S terminal of the latch, and the R terminal of the latch is electrically connected to the driver. The two ends of the output buffer driver are electrically connected to the comparators, one of which is electrically connected to the CS1 pin and the other is electrically connected to the CS2 pin. The O terminal of the latch is electrically connected to the PWM generator.

[0015] In this application, the AC voltage first passes through inductor L2 and is then converted into a pulsating DC voltage via a full-bridge rectifier (D1-D4). Next, the filtering stage consisting of L1, C1, and C2 further smoothes the pulsating voltage, providing a relatively clean DC input to the driver module. Resistors R1, R2, R3, R4, R5, and R6, along with capacitors C2 and C3, form the feedback network. The voltage divided by R1 and R3 is fed to the driver module's CS1 pin as primary current feedback. The network of R2, R5, and R6 is used for overcurrent protection or auxiliary current regulation and is connected to the CS2 pin. These feedback signals are used to dynamically adjust the PWM duty cycle within the driver module to maintain a constant LED current. The oscillator OSC sets the circuit's operating frequency, and its signal is processed by a latch and fed to the PWM generator. The latch's state is controlled by an external setting (such as the RT pin) and a feedback signal. A comparator compares the voltages on the CS1 and CS2 pins with an internal reference to achieve precise adjustment of the PWM duty cycle. The PWM signal controls the switch (directly controlling a MOSFET or IGBT through the driver), thereby regulating the average current flowing into the LED. Transistor Q1 acts as a current sensing or short-circuit protection element, working in conjunction with R2. If the output current exceeds the limit, Q1's state changes, affecting the signal at the GATE pin and thus adjusting the driver's output. Capacitor C3 provides decoupling and stabilization at the VDD pin, ensuring a clean power supply to the driver module.

[0016] In a specific embodiment, a high-efficiency constant-current driver circuit is designed for indoor LED lighting applications. The goal is to drive a string of 10 high-brightness LEDs in series, with each LED having a forward voltage of approximately 3V and a total voltage of approximately 30V. The required constant current is 700mA.

[0017] Input power: 220V AC voltage;

[0018] Input filter module: Inductor L2 is selected as 1μH, which is used for primary filtering and smoothing AC input.

[0019] D1-D4 use fast recovery diodes, such as MBR1045, to build a full-bridge rectifier.

[0020] C1 and C2 are each 100μF / 400V electrolytic capacitors, which together with L1 (100μH) form the second stage of filtering and output a smooth DC voltage.

[0021] Driver module: The oscillator OSC is set to 100kHz operating frequency and can be adjusted by the external resistor RT.

[0022] The latch receives the oscillating signal and adjusts its state based on the feedback from the CS1 and CS2 pins.

[0023] The PWM generator generates a PWM signal with controllable duty cycle according to the latch output.

[0024] Comparators monitor CS1 and CS2 respectively and compare them with the internal reference voltage for precise regulation.

[0025] The voltage regulator provides a stable operating voltage for the internal circuits.

[0026] The driver controls the LED current through a MOSFET (such as IRFZ44N).

[0027] Feedback and Protection:

[0028] R1 = 10kΩ, R3 = 10kΩ, after voltage division, connected to CS1 as the main feedback to set the desired current level.

[0029] R2 = 1kΩ, R5 = 10kΩ, R6 = 10kΩ, forming an auxiliary feedback path to CS2 for overcurrent protection.

[0030] Q1 is a small signal transistor (such as BC547). When the output current is too large, the voltage drop across R2 increases, Q1 turns on, affecting the GATE signal, thereby reducing the PWM duty cycle and protecting the circuit.

[0031] C3 is a 100nF ceramic capacitor that decouples the VDD pin to ensure pure power supply.

[0032] Output filtering: The output is directly connected to the LED load, assuming that the LED array itself has a certain inductance and ESR (equivalent series resistance) that are sufficient to suppress the ripple.

[0033] Circuit adjustment and testing:

[0034] By adjusting the RT resistor value, the oscillation frequency can be fine-tuned, affecting the efficiency and output ripple.

[0035] The ratio of R1 to R3 determines the target current level and can be adjusted according to the actual LED array requirements.

[0036] After implementing the circuit, use an oscilloscope to measure the LED current ripple to ensure that the current fluctuation rate is less than 10% to verify the constant current characteristic.

[0037] Test the overcurrent protection function by simulating short circuit or overload conditions to see if Q1 can respond in time and protect the circuit from damage.

[0038] This embodiment demonstrates how to specifically apply the technical solution of the present application. By carefully selecting components and optimizing parameters, a high-efficiency, high-stability LED driving solution is achieved, which is suitable for indoor lighting applications and effectively solves the problems of low efficiency and insufficient protection existing in traditional driving solutions.

[0039] This application significantly improves power conversion efficiency and reduces power consumption through advanced PWM modulation and precise current control. A precise feedback control mechanism ensures that the LED current is unaffected by power supply voltage fluctuations and load variations, maintaining consistent brightness and extending LED life. Built-in overcurrent protection and short-circuit protection mechanisms increase system reliability and safety. The external resistor network (e.g., RT, R1-R6) can be adjusted to accommodate different LED load requirements, providing flexibility in a variety of applications.

[0040] Although the embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations may be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A high-efficiency constant-current LED driving circuit, characterized in that: The device comprises an input filter module and a driving module. The input filter module comprises diodes D1-D4 and inductors L1, L2, capacitors C1, C2, and a voltage input terminal. The voltage input terminal is electrically connected to the input terminal of the inductor L2. The output terminal of the inductor L2 is electrically connected to the anodes of the diodes D2 and D3, respectively. The cathode of the diode D2 is electrically connected to one end of the capacitor C1 and the anode of the diode D1, respectively. The cathode of the diode D1 is electrically connected to the anode of the diode D4 and one end of the capacitor C2, respectively. The cathode of the diode D4 is electrically connected to the input terminal of the inductor L1. The input filter module is used to convert the AC voltage into a smooth DC voltage. The driving module comprises an oscillator OSC, a latch, a PWM generator, a comparator, a voltage regulator, and a driver. The driving module is used to control the duty cycle of the internal switch to adjust the output current and keep the LED current constant. The LED load array is connected to the output terminal of the driving module.

2. The high-efficiency constant-current LED driving circuit according to claim 1, characterized in that: The output end of the inductor L1 is electrically connected to the other end of the capacitor C1 and the collector of a transistor Q1. The base of the transistor Q1 is electrically connected to the GATE pin of the driving module. The cathode of the diode D3 is electrically connected to the resistor R2 and the emitter of the transistor Q1.

3. The high-efficiency constant-current LED driving circuit according to claim 2, characterized in that: The resistor R2 is electrically connected to the resistor R5, the resistor R5 is electrically connected to the CS2 pin of the driving module, and the resistor R5 is further electrically connected to a resistor R6, which is grounded.

4. The high-efficiency constant-current LED driving circuit according to claim 3, characterized in that: One end of the capacitor C2 and the resistor R1 is also electrically connected to a resistor R3, and the other end of the resistor R3 is electrically connected to the CS1 pin of the driving module and a resistor R4 respectively. The resistor R4 is electrically connected to the capacitor C3, and the capacitor C3 is electrically connected to the VDD pin of the driving module.

5. The high-efficiency constant-current LED driving circuit according to claim 1, characterized in that: The driving module includes an oscillator OSC, a latch, a PWM generator, a comparator, a voltage regulator, and a driver. One end of the oscillator OSC is electrically connected to the RT pin, the other end of the oscillator OSC is connected to the S end of the latch, the R end of the latch is electrically connected to the driver, and the two ends of the output buffer driver are respectively electrically connected to the comparators, one of the comparators is electrically connected to the CS1 pin, and the other comparator is electrically connected to the CS2 pin. The O end of the latch is electrically connected to the PWM generator.

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