Slow-starting and slow-extinguishing circuit and LED power supply device

Abstract

The invention relates to the technical field of non-intelligent lighting control, in particular to a slow-starting and slow-extinguishing circuit and an LED power supply device. The circuit comprises an input filtering rectification module, a power factor correction module, a capacitor energy storage module, a master control parameter adjustment module and a flyback isolation dimmable circuit. The input filter rectifier module and the power factor correction module convert alternating current into stable direct current and improve power factors, and the capacitor energy storage module provides temporary power supply for elements such as a single-chip microcomputer after power failure through a large-capacity capacitor and a voltage stabilizing chip, so that light is slowly extinguished. The main control parameter adjustment module sets slow start time and duty ratio by using a dial switch, outputs a PWM signal through a single-chip microcomputer to control the flyback dimming module, and combines a flyback transformer and a feedback circuit to realize LED brightness dynamic adjustment and constant current output. Slow starting and slow extinguishing of light are achieved through the pulse width modulation technology, the slow extinguishing time is prolonged through the high-capacity capacitor, and the flexibility of the lighting system and the user experience are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of intelligent lighting control, and more specifically, to a soft-start and soft-turn-off circuit and an LED power supply device. Background Art

[0002] The development of LED lighting technology has witnessed the evolution from simple indicator light applications to the current widespread use in various lighting scenarios. In the early days, due to low luminous efficiency and insufficient brightness, LEDs were mainly used for indicating the status of electronic devices. With the progress of semiconductor material technology, especially the invention and commercialization of blue LEDs, high-brightness white LEDs have become possible, greatly expanding their application scope. On this basis, Pulse Width Modulation (PWM) technology has been introduced into LED driver design to achieve precise control of the brightness of LED lights, further improving the energy efficiency ratio and user experience.

[0003] In the field of LED lighting, although traditional drive solutions can achieve basic brightness adjustment and power conversion, there are obvious shortcomings in dynamic dimming accuracy and functional extensibility after power-off. For example, in theater lighting control or intelligent building systems, the lights need to achieve smooth brightness gradients according to scene requirements. However, in existing PWM dimming technologies, due to a single control signal or insufficient feedback mechanism, obvious brightness steps and excessive harshness often occur. In addition, the energy storage design of traditional solutions is difficult to maintain stable power supply after power-off, resulting in problems such as short soft-turn-off time. Summary of the Invention

[0004] The purpose of the present invention is to provide a soft-start and soft-turn-off circuit and an LED power supply device to solve the problems that traditional LED drive solutions are insufficient in dynamic dimming accuracy and difficult to maintain stable power supply after power-off, resulting in a short soft-turn-off time.

[0005] To achieve the above purpose, a soft-start and soft-turn-off circuit and an LED power supply device are provided, including an input filter rectification module, a power factor correction module, and a flyback dimming module, and further including a capacitor energy storage module and a main control parameter adjustment module, where: The input end of the input filter rectification module is connected to an AC power supply, and the output end is connected to the input end of the power factor correction module; The output end of the power factor correction module is connected to the input end of the capacitor energy storage module; The output end of the capacitor energy storage module is connected to the input end of the main control parameter adjustment module, which includes a large-capacity electrolytic capacitor C4 for providing electrical energy to the main control parameter adjustment module after power-off; The main control parameter adjustment module is communicatively connected to the dimming signal end of the flyback dimming module for adjusting the PWM dimming duty cycle; The flyback dimming module integrates an LED drive function and directly provides a stable drive current for the LED load.

[0006] In the above technical solution, through the electrolytic capacitor C4 and the voltage regulator chip Q2 / U2 of the capacitor energy storage module, after the input power is disconnected, the electric energy stored in the electrolytic capacitor C4 can continuously supply power to the microcontroller U3 and the control chip U4 for a short time, supporting the complete PWM dimming attenuation process. The main control parameter adjustment module sets the soft start time and PWM duty cycle through the dip switch SW1, and the microcontroller U3 outputs a nonlinear S-shaped dimming curve to achieve a smooth transition of brightness and avoid the step-like mutation of the traditional solution.

[0007] On this basis, the pin 7 of the control chip U4 is connected to the primary winding of the transformer T1 through the series-connected resistors R17 and R15, the other end of the primary winding of the transformer T1 is connected to the anode of the diode D8, and the cathode of the diode D8 is connected to the primary winding of the transformer T1 through the parallel-connected resistor R33, the resistor R14 and the capacitor C7; Pin 7 of the control chip U4 is connected to the cathode of the diode D9, the anode of the diode D9 is connected to the resistor R18, the other end of the resistor R18 is connected to the primary auxiliary winding of the transformer T1, and the other end of the primary auxiliary winding of the transformer T1 is grounded; The other end of the resistor R18 is also connected to the resistor R19, the pin 3 of the control chip U4 and the other end of the resistor R19 are connected to the anode of the diode D10, the capacitor C17 and the resistor R35, the cathode of the diode D10 is grounded through the resistor R22, and the other ends of the capacitor C17 and the resistor R35 are both grounded.

[0008] This technical solution detects output voltage or current changes through a feedback circuit set on the primary auxiliary winding side of transformer T1, and sends the feedback signal back to the control chip U4, so that the control chip U4 adjusts the drive signal to maintain the stable output of the primary winding of transformer T1, thereby realizing constant current control during the dimming process.

[0009] Compared with the prior art, the present invention has the following beneficial effects: 1. In the slow start and slow off circuit and LED power supply device, the pulse width modulation signal output by the single chip microcomputer controls the flyback dimming module, which can accurately and dynamically adjust the brightness of the LED lamp. With the preset PWM attenuation curve, the slow start and slow off of the light can be achieved, avoiding the problems of obvious brightness steps and abrupt transitions in traditional solutions, and improving user experience.

[0010] 2. In the slow start and slow turn off circuit and LED power supply device, the large-capacity capacitor in the capacitor energy storage module provides temporary power supply for the microcontroller and related chips after power failure, so that the light can remain on for a certain period of time before being turned off after the input power is turned off, solving the problem of the inability to slow down the turn off time in traditional solutions. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is the overall structural block diagram of the present invention; Figure 2 It is the circuit diagram of the input filter rectification module and the power factor correction module of the present invention; Figure 3 It is the circuit diagram of the capacitor energy storage module and the main control parameter adjustment module of the present invention; Figure 4 It is the circuit diagram of the flyback dimming module of the present invention; Specific embodiments Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0012] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus cannot be understood as a limitation to the present invention.

[0013] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, "a plurality" means two or more, unless otherwise specifically defined.

[0014] Please refer to Figure 1As shown in the figure, the purpose of this embodiment is to provide a soft-start and soft-turn-off circuit and an LED power supply device, including an input filter rectification module, a power factor correction module, a capacitor energy storage module, a main control parameter adjustment module, and a flyback dimming module. The input end of the input filter rectification module is connected to an AC power supply, and the output end is connected to the input end of the power factor correction module. The output end of the power factor correction module is connected to the input end of the capacitor energy storage module. The output end of the capacitor energy storage module is connected to the input end of the main control parameter adjustment module, which includes a large-capacity electrolytic capacitor C4 for supplying electrical energy to the main control parameter adjustment module after power-off. The main control parameter adjustment module is communicatively connected to the dimming signal end of the flyback dimming module for adjusting the PWM dimming duty cycle. The flyback dimming module integrates the LED driving function and directly provides a stable driving current for the LED load.

[0015] As Figure 2 shown, the input end of the input filter rectification module accesses the AC power supply through the neutral terminal L and the live terminal N. The neutral terminal L and the live terminal N are respectively connected to two pins at the input end of the common-mode inductor L1. The common-mode inductor L1 can suppress common-mode interference, prevent interference in the power grid from entering the circuit, and also prevent interference generated by the circuit itself from being fed back to the power grid. An X capacitor CX1 and a varistor RV1 are connected in parallel on the input side of the common-mode inductor L1. The X capacitor CX1 is used to filter out differential-mode interference and cooperate with the common-mode inductor L1 to improve the anti-interference ability of the power supply input. The varistor RV1 is used to suppress input overvoltage. When the input voltage is too high, its resistance value rapidly decreases, introducing the excessive voltage to the ground to protect subsequent circuit components from being damaged by overvoltage. The AC input terminals of the rectifier bridge DB1 are respectively connected to the output end of the common-mode inductor L1. One end is connected to the input bus of the power factor correction module through an inductor L3, and a resistor R6 is connected in parallel with the inductor L3. The DC output terminal is connected in parallel with a capacitor C1, one end of which is connected to the input bus of the power factor correction module, and the other end is grounded.

[0016] In the power factor correction module, the model of the APFC control chip U1 is BP2636C. The current output by the rectifier bridge DB1 passes through the inductor L2 and then is output through the diode D1. The diode D1 is a boost diode, which, when the power factor correction module is working, cooperates with the inductor L3 to achieve the boost function. A capacitor C13 is connected in parallel outside the inductor L2 and the diode D1. The DRAIN pin of the APFC control chip U1 is connected between the inductor L2 and the diode D1. The VCC pin of the APFC control chip U1 is connected to the output end of the rectifier bridge DB1 through a resistor R25 and a resistor R28, and is also connected to the anode of the diode D4 and the capacitor C2, and then connected to the 10V power supply through a resistor R37. The diode D4 is used for the auxiliary power supply of the circuit, and the capacitor C2 plays roles such as filtering and energy storage to stabilize the working voltage of the circuit.

[0017] As Figure 3As shown, the input terminal of the voltage regulator chip Q2 / U2 (model number HT7550 or 78L05) is connected to the high-voltage output terminal of the power factor correction module through the resistor R27. The other end of the resistor R27 is connected to the Vin pin of the voltage regulator chip Q2 / U2 after being divided by the resistor R23. At the connection node between the resistor R23 and the power factor correction module, a large-capacity electrolytic capacitor C4 (68 μF / 400V, 450V or 82 μF / 400V, 450V) is connected in parallel. Its positive electrode is connected to the high-voltage terminal, and the negative electrode is directly grounded, which is used for energy temporary storage after the main power supply is cut off. The input terminal of the voltage regulator chip Q2 / U2 is also connected to the cathodes of the diodes D2 and D3 and the positive electrode of the electrolytic capacitor C3. The negative electrode of C3 and the GND pin of the voltage regulator chip Q2 / U2 are grounded together. When the main power supply is disconnected, the energy stored in C4 discharges to C3 through D2, and after being regulated by the voltage regulator chip Q2 / U2, a 5V continuous power supply is output.

[0018] The power supply pin 4 of the single-chip microcomputer U3 (model number CIU32F003) is directly connected to the 5V output terminal of the voltage regulator chip Q2 / U2. The parallel ceramic capacitor C15 and electrolytic capacitor C5 are used for high-frequency and low-frequency filtering. Its pin 6 is connected to the output terminal of the voltage regulator chip Q2 / U2 through the pull-up resistor R2, and at the same time is connected to the common terminal of the DIP switch SW1. The 1-4 bits of SW1 are grounded through the resistors R1 (51 kΩ), R3 (2.2 kΩ), R5 (51 kΩ), and R8 (2.2 kΩ) respectively, forming a 4-bit binary code input, which is used to set the soft-start time. The pull-down resistor R9 ensures that the pin 6 remains at a low level when it is floating.

[0019] The pin 5 of the single-chip microcomputer U3 outputs a PWM dimming signal. After filtering out high-frequency noise through the RC filter network, it is clamped to the base of the triode Q1 through the diode D6. The emitter of Q1 is grounded, and the collector is pulled up to the voltage-dividing network composed of the resistors R11 and R10 through the resistor R12, and finally connected to the power supply zero line. When the AC power supply is turned on, Q1 conducts, causing the pin 1 to detect a high level, triggering the single-chip microcomputer to start the soft-brightening process; when the power is off, Q1 cuts off, and the level of the pin 1 returns to zero, starting the preset PWM attenuation soft-extinguishing program.

[0020] As Figure 4As shown in the figure, the flyback isolated dimmable circuit includes a control chip U4 of model BP3176. Its pin 8 is pulled down to ground through capacitor C9 and is also connected to a parallel filter network composed of C12 and electrolytic capacitor C10 to receive an externally input pulse width modulation signal, which is used to adjust the output current or voltage to achieve the dimming function. The chip drive signal is output from pin 5 (DRV), controls the conduction and turn-off of the power switch tube, and is transmitted to the left pin of the primary winding of transformer T1 through series resistors R17 and R15. The right end of the primary winding is connected to the anode of fast recovery diode D8, and its cathode forms a closed loop through an RC absorption circuit composed of R33, R14, and C7 to suppress the voltage spike on the primary winding of the transformer and protect the switch tube.

[0021] Transformer T1 is a flyback transformer that plays the role of electrical isolation and energy transfer. Its primary auxiliary winding provides auxiliary power supply for the chip through diode D9 and current limiting resistor R18. The cathode of D9 is connected to pin 8 of U4, the anode is connected to the upper pin of the auxiliary winding through R18, and the lower end is directly grounded to form an auxiliary power supply loop. The dimming control signal is introduced from the PWM input port, transmitted through R19 to pin 3 of U4, and at the same time, through a low-pass filter network composed of D10, C17, and R35, the external PWM signal is converted into a DC level so that the dimming signal can smoothly control the brightness of the LED.

[0022] In the secondary side circuit, after the secondary winding of transformer T1 is rectified by Schottky diode D7, it is filtered by electrolytic capacitor C8 and output to the LED+ terminal. The parallel resistors R34 and C16 in the LED- loop absorb the spike voltage, and R36, R16 are the discharge resistors of C8. Y capacitors CY1 and CY2 are respectively connected across the secondary reference ground (SND terminal) and the positive and negative poles of the LED load. One end of CY1 is connected to the SND terminal, and the other end is connected to LED+; CY2 also uses the SND terminal as the common point, and the other end is connected to LED+. The high-frequency common-mode noise on the LED line is conducted back to the secondary ground through a low-impedance path, effectively suppressing electromagnetic radiation and ensuring that the circuit meets the EMC standard.

Claims

1. A soft-start and soft-turn-off circuit, comprising an input filter rectification module, a power factor correction module and a flyback dimming module, characterized in that: It also includes a capacitive energy storage module and a main control parameter adjustment module, where: The input end of the input filter rectification module is connected to an AC power supply, and the output end is connected to the input end of the power factor correction module; The output end of the power factor correction module is connected to the input end of the capacitive energy storage module; The output end of the capacitive energy storage module is connected to the input end of the main control parameter adjustment module, which includes a large-capacity electrolytic capacitor C4 for supplying electrical energy to the main control parameter adjustment module after power failure; The main control parameter adjustment module is communicatively connected to the dimming signal end of the flyback dimming module for adjusting the PWM dimming duty cycle; The flyback dimming module integrates the LED driving function and directly provides a stable driving current for the LED load.

2. The soft start and soft turn-off circuit according to claim 1, wherein: The capacitive energy storage module also includes a voltage regulator chip Q2 / U2. The input end of the voltage regulator chip Q2 / U2 is connected to a resistor R27, and the other end of the resistor R27 is connected to the output end of the power factor correction module through a resistor R23. The connection between the resistor R23 and the power factor correction module is also connected to the positive electrode of the electrolytic capacitor C4, and the negative electrode of the electrolytic capacitor C4 is grounded; The input end of the voltage regulator chip Q2 / U2 is also connected to the cathode of a diode D2, the cathode of a diode D3, and the positive electrode of an electrolytic capacitor C3. The negative electrode of the electrolytic capacitor C3 is connected to the anode of the diode D3 and the grounding end of the voltage regulator chip Q2 / U2. The grounding end of the voltage regulator chip Q2 / U2, the anode of the diode D3, and the negative electrode of the electrolytic capacitor C3 are all grounded.

3. The soft start and soft turn-off circuit according to claim 2, characterized in that: The main control parameter adjustment module includes a single-chip microcomputer U3. The power supply pin 4 of the single-chip microcomputer U3 is connected to the output end of the voltage regulator chip Q2 / U2, and a capacitor C15 and a capacitor C5 are also connected in parallel therebetween. The other ends of the capacitor C15 and the capacitor C5 are both grounded.

4. The slow start and slow extinguish circuit according to claim 3, characterized in that: The pin 6 of the single-chip microcomputer U3 is connected to the input end of a DIP switch SW1. The DIP switch SW1 includes multiple independent bits, where the 1st, 2nd, 3rd, and 4th bits are respectively connected to resistors R1, R3, R5, and R8. The other ends of the resistors R1, R3, R5, and R8 are all grounded. The pin 6 of the single-chip microcomputer U3 is also connected to a pull-up resistor R2 and a pull-down resistor R9, and the resistor R2 is connected to the output end of the voltage regulator chip Q2 / U2.

5. The slow start and slow extinguish circuit according to claim 3, wherein: The pin 1 of the single-chip microcomputer U3 is connected to a capacitor C6, a resistor R13, and the emitter of a triode Q1. The other ends of the capacitor C6 and the resistor R13 are both connected to the anode of a diode D6. The other ends of the capacitor C6 and the resistor R13 and the anode of the diode D6 are all grounded. The cathode of the diode D6 is connected to the base of the triode Q1 and a resistor R12. The collector of the triode Q1 is connected to the other end of the resistor R12 and a resistor R11. The other end of the resistor R11 is connected to a resistor R10, and the other end of the resistor R10 is connected to the power supply zero line.

6. The slow start and slow extinction circuit according to claim 1, characterized in that: The flyback dimming module includes a control chip U4. The pin 8 of the control chip U4 is connected to a capacitor C9, and the pin 7 of the control chip U4 is connected to a capacitor C12. The capacitor C12 is also connected in parallel with an electrolytic capacitor C10. The negative electrodes of the capacitor C9, the capacitor C12, and the electrolytic capacitor C10 are all grounded.

7. The soft start and soft turn-off circuit according to claim 6, characterized in that: Pin 8 of the control chip U4 is connected to the primary winding of the transformer T1 through the series-connected resistors R17 and R15. The other end of the primary winding of the transformer T1 is connected to the anode of the diode D8. The cathode of the diode D8 is connected to the primary winding of the transformer T1 through the parallel-connected resistors R33, R14, and the capacitor C7.

8. The soft start and soft extinction circuit according to claim 6, characterized in that: Pin 8 of the control chip U4 is connected to the cathode of the diode D9. The anode of the diode D9 is connected to the resistor R18. The other end of the resistor R18 is connected to the primary auxiliary winding of the transformer T1. The other end of the primary auxiliary winding of the transformer T1 is grounded.

9. The slow start and slow extinction circuit according to claim 8, wherein: The other end of the resistor R18 is also connected to the resistor R19. Pin 3 of the control chip U4 and the other end of the resistor R19 are connected to the anode of the diode D10, the capacitor C17, and the resistor R35. The cathode of the diode D10 is grounded through the resistor R22. The other ends of the capacitor C17 and the resistor R35 are both grounded.

10. An LED power supply device, characterized in that: It includes a housing, wherein: There is a circuit board inside the housing. The circuit board is integrated with an input filter rectification module, a power factor correction module, a capacitor energy storage module, a main control parameter adjustment module, and a flyback dimming module. One end of the housing is provided with an AC input interface, including a neutral terminal and a live terminal. The other end of the housing is provided with a DC output interface, including an LED+ port and an LED- port.

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