A silicon controlled PWM LED dimming circuit

Abstract

The utility model discloses a silicon controlled rectifier PWM's LED light modulation circuit, including power module, voltage increasing circuit, flyback voltage reducing circuit, silicon controlled rectifier detection circuit, silicon controlled rectifier light modulation transfer analog light modulation circuit, analog light modulation transfer PWM light modulation circuit and auxiliary power supply circuit, through main power path and control signal path double -channel isolation design, and the main power path is coordinated to realize high -efficient energy conversion by voltage increasing circuit and flyback voltage reducing circuit after power module rectification, and control signal path extracts the conduction angle signal through silicon controlled rectifier detection circuit, generates PWM light modulation signal through two -stage signal conversion circuit, and combines photo -coupler isolation and discrete component circuit to eliminate signal interference. The utility model solves the technical problem of poor compatibility of silicon controlled rectifier light modulation and PWM light modulation, large circuit volume and low efficiency in the prior art.

Description

Technical Field

[0001] This utility model relates to the field of LED driver circuit technology, and in particular to an LED dimming circuit that converts a silicon controlled rectifier to a PWM converter. Background Technology

[0002] Most dimming power supplies on the market currently employ a single dimming protocol, such as 0-10V dimming, SCR dimming, PWM dimming, and wireless dimming. These protocols are incompatible with traditional SCR dimmers and high-precision digital dimming requirements, necessitating the configuration of multiple independent dimming devices for different scenarios, increasing system cost and complexity. Traditional SCR dimmers are designed for incandescent lamps, relying on the characteristics of holding current and load impedance. Incandescent lamps depend on a stable holding current for conduction, while the high impedance of LED drivers can easily cause false triggering of the SCR, resulting in flickering at low brightness or limited dimming range. Although PWM dimming can achieve high-precision flicker-free control through duty cycle adjustment, it relies on a dedicated controller, making it difficult to directly adapt to existing SCR dimming systems. To address these contradictions, existing technologies attempt to integrate flicker-reduction functionality through a single-stage flyback topology, but this requires large-capacity electrolytic capacitors to suppress low-frequency ripple, leading to a significant increase in circuit size and cost. Furthermore, the high heat generation of the flicker-reduction chip complicates the design. Another approach proposes converting the SCR conduction angle signal into an analog dimming signal, but the conversion accuracy is affected by noise and stability is insufficient at low brightness. These improvements do not fundamentally solve the core problems of poor dimming mode compatibility and the trade-off between circuit size and efficiency, forcing users to compromise between functionality, cost, and performance. Therefore, there is an urgent need for an LED driver solution that is compatible with traditional SCR dimmers, supports PWM output, and achieves a highly efficient and compact design. Utility Model Content

[0003] The main purpose of this invention is to propose a thyristor-to-PWM LED dimming circuit, which aims to solve the technical problems of poor compatibility between thyristor dimming and PWM dimming, large circuit size and low efficiency in the prior art.

[0004] To achieve the above objectives, the first aspect of this utility model proposes a thyristor-to-PWM LED dimming circuit, including a power supply module, a boost circuit, a flyback buck circuit, a thyristor detection circuit, a thyristor-to-analog dimming circuit, an analog dimming-to-PWM dimming circuit, and an auxiliary power supply circuit. The power module has an input terminal connected to a thyristor dimmer, used to convert phase-cut AC power into a primary DC voltage. A boost circuit's input terminal is connected to the output terminal of the power module, used to boost the primary DC voltage into a high-voltage DC voltage. A flyback buck circuit's input terminal is connected to the output terminal of the boost circuit, used to convert the high-voltage DC voltage into a first DC voltage to power the LED load. A thyristor detection circuit's input terminal is connected to the AC side of the power module, used to extract the thyristor conduction angle signal and generate a square wave signal. A thyristor dimming-to-analog dimming circuit's input terminal is connected to the output terminal of the thyristor detection circuit, used to convert the square wave signal into an analog voltage signal. An analog dimming-to-PWM dimming circuit's input terminal is connected to the output terminal of the thyristor dimming-to-analog dimming circuit, and its output terminal is connected to the PWM control terminal of the flyback buck circuit, used to convert the analog voltage signal into a PWM control signal. An auxiliary power supply circuit's input terminal is connected to the output terminal of the boost circuit, used to convert the high-voltage DC voltage into a second DC voltage to power the control module in the circuit.

[0005] Preferably, the thyristor detection circuit includes a voltage reference chip, a first transistor, a first MOSFET, and an optocoupler; the reference terminal of the voltage reference chip is connected to the AC input terminal of the power supply module, used to detect the thyristor conduction angle signal, and generates a square wave signal at the output terminal; the emitter of the first transistor is connected to the output terminal of the auxiliary power supply circuit, and the base is connected to the output terminal of the voltage reference chip, used to amplify the square wave signal; the gate of the first MOSFET is connected to the collector of the first transistor, the drain is connected to the output terminal of the auxiliary power supply circuit and the first input terminal of the optocoupler, and the source and the second input terminal of the optocoupler are grounded; the output terminal of the optocoupler generates an isolated square wave signal.

[0006] Preferably, the analog dimming to PWM dimming circuit includes a dimming conversion chip; the first input terminal of the dimming conversion chip is connected to the output terminal of the auxiliary power supply circuit, and the second input terminal is connected to the output terminal of the thyristor dimming to analog dimming circuit; the first output terminal of the dimming conversion chip is connected to the PWM control terminal of the flyback buck circuit, used to convert the analog voltage signal into a PWM control signal and adjust the LED load current.

[0007] Preferably, the thyristor-controlled dimming to analog dimming circuit includes a second transistor, a first resistor, and a filter and rectifier circuit; the first output terminal of the optocoupler is connected to the second output terminal of the dimming conversion chip through the first resistor; the second output terminal of the optocoupler is grounded, and the first output terminal is connected to the base of the second transistor through the filter and rectifier circuit; the collector of the second transistor is connected to the second output terminal of the dimming conversion chip, and the emitter is connected to the second input terminal of the dimming conversion chip.

[0008] Preferably, the flyback buck circuit includes a dimming control chip, a first transformer, and a second MOSFET; the first input terminal of the dimming control chip is connected to the output terminal of the boost circuit, the second input terminal is connected to the output terminal of the analog dimming to PWM dimming circuit, and the driving terminal is connected to the gate of the second MOSFET; the first end of the primary winding of the first transformer is connected to the output terminal of the boost circuit, and the second end is connected to the drain of the second MOSFET; the source of the second MOSFET is grounded.

[0009] Preferably, the flyback buck circuit further includes a third transistor, a first diode, and a second diode; the anode of the first diode is connected to the first end of the auxiliary winding of the first transformer, and the second end of the auxiliary winding of the first transformer is grounded; the collector of the third transistor is connected to the cathode of the first diode, the emitter is connected to the first input terminal of the dimming control chip, and the base is connected to the anode of the second diode; the cathode of the second diode is grounded.

[0010] Preferably, the flyback buck circuit further includes a voltage detection circuit and a current detection circuit; the voltage detection circuit includes a second resistor, a third resistor, and a first capacitor, the first end of the second resistor is connected to the first end of the auxiliary winding of the first transformer, the second end of the second resistor, the first end of the third resistor, and the first end of the capacitor are all connected to the third input terminal of the dimming control chip, and the second end of the third resistor and the second end of the capacitor are grounded; the current detection circuit includes a fourth resistor, a fifth resistor, and a second capacitor, the first end of the fourth resistor and the first end of the second capacitor are all connected to the fourth input terminal of the dimming control chip, the second end of the fourth resistor and the first end of the fifth resistor are all connected to the source of the second MOSFET, and the second end of the fifth resistor and the second end of the second capacitor are grounded.

[0011] Preferably, the circuit further includes an output rectifier circuit, which comprises dual diodes, a first inductor, a primary filter circuit, and a secondary filter circuit. The first end of the dual diodes is connected to the output terminal of the flyback buck circuit, and the second end of the dual diodes is connected to the first input terminal of the first inductor. The second input terminal of the first inductor is grounded, and its output terminal is used to power the LED load. The primary filter circuit is connected between the first and second ends of the dual diodes, and the secondary filter circuit is connected between the second end of the dual diodes and ground.

[0012] Preferably, the boost circuit includes an APFC control chip, a second inductor, a third MOSFET, a fourth capacitor, and a third diode; the first terminal of the second inductor, the anode of the third diode, and the drain of the third MOSFET are all connected to the output terminal of the power module; the second terminal of the second inductor and the cathode of the third diode are all connected to the first terminal of the fourth capacitor; the first input terminal of the APFC control chip is connected to the output terminal of the auxiliary power supply circuit, and the driving terminal is connected to the gate of the third MOSFET; the source of the third MOSFET is grounded.

[0013] Preferably, the power module includes a rectifier bridge, a fourth diode, a sixth resistor, and a fourth MOSFET; the first DC output terminal of the rectifier bridge is connected to the gate of the fourth MOSFET and the cathode of the fourth diode, the second DC output terminal of the rectifier bridge is connected to the anode of the fourth diode, the first terminal of the sixth resistor, and the source of the fourth MOSFET, and the drain of the fourth MOSFET and the second terminal of the sixth resistor are grounded.

[0014] This invention proposes a thyristor-to-PWM LED dimming circuit. The power module converts the phase AC power cut by the thyristor dimmer into a primary DC voltage, which is then boosted by a boost circuit and input to a flyback buck circuit to form the main power path. The thyristor detection circuit extracts the conduction angle signal from the AC side of the power module, which is then converted into a PWM control signal through a thyristor-to-analog dimming circuit and an analog-to-PWM dimming circuit, forming an isolated control signal path. The two paths operate independently and are isolated by optocouplers to block interference, allowing for compatibility with thyristor dimmers and achieving full-range dimming from 1% to 100%. The boost circuit is implemented using an APFC control chip. Power factor correction and high-voltage boost: The flyback buck circuit precisely adjusts the LED current through PWM control. The two-stage circuit works together to reduce output ripple. The main power path can suppress flicker without large-capacity electrolytic capacitors, improving conversion efficiency. The auxiliary power supply circuit extracts a stable low-voltage power supply from the high-voltage side of the boost circuit to provide isolated power to the control module, avoiding signal path interference from the main power. Through the coordinated work of the boost circuit and the flyback buck circuit, the output rectifier circuit only needs small-capacity electrolytic capacitors for filtering, which can effectively improve conversion efficiency and reduce losses. Compared with the traditional single-stage flyback flicker-eliminating IC circuit solution, the two-stage solution is more cost-effective, more efficient, and smaller in size.Furthermore, the thyristor detection circuit accurately extracts the conduction angle signal through a voltage reference chip and a cascaded transistor-MOSFET structure, and combines optocoupler isolation to achieve high anti-interference square wave signal conversion, effectively eliminating signal distortion caused by dimmer impedance differences; the analog-to-PWM dimming circuit directly achieves linear conversion from analog to PWM signals through a dimming conversion chip, using isolated power supply and internal chip algorithms to eliminate signal distortion, ensuring high precision and anti-interference of dimming control; the thyristor-to-analog dimming circuit filters out signal noise and stabilizes the output through a filter rectifier network and a transistor buffer structure, using discrete components to achieve high-precision conversion from square wave to analog voltage; the flyback buck circuit achieves precise LED current regulation through the coordinated control of the dimming control chip and PWM signal, and combined with the high-efficiency energy conversion structure of the transformer and MOSFET, it can simplify the driving logic while reducing output ripple, suppressing flicker and improving overall conversion efficiency without the need for large-capacity filter components; the flyback buck circuit achieves self-powered operation through an auxiliary winding and a transistor voltage regulator structure, and uses diodes and a reference voltage to stabilize the control chip. The power supply simplifies the power supply circuit while improving system reliability and preventing chip damage caused by high voltage fluctuations. Voltage and current detection circuits perform voltage division sampling and filtering network feedback for accurate output status feedback. Combined with dual-loop closed-loop control, the PWM duty cycle is dynamically adjusted to improve LED current control accuracy. The output rectifier circuit adopts a dual-diode full-wave rectification and inductor filtering design. The primary and secondary dual-filter structure effectively suppresses high-frequency ripple, achieving small-capacity filtering while reducing component count, minimizing power supply ripple, and reducing circuit size. The boost circuit uses an APFC control chip to drive an inductor-MOSFET topology for high-efficiency power factor correction. Combined with diode and capacitor synergy, it stably outputs high-voltage DC over a wide voltage input range, improving overall energy efficiency while reducing grid harmonic interference. It boasts strong compatibility and a compact structure. The power module suppresses thyristor conduction surge current through an active damping circuit and uses MOSFETs and diodes to protect the rectifier bridge from voltage spikes. Combined with a two-stage EMI filtering design, it effectively suppresses noise and provides system safety protection, reducing component costs and improving reliability.

[0015] In summary, this invention solves the technical problems of poor compatibility between thyristor dimming and PWM dimming, as well as the large circuit size and low efficiency in the prior art. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0017] Figure 1 This is a circuit block diagram of a silicon controlled rectifier to PWM LED dimming circuit according to the present invention.

[0018] Figure 2 This is a circuit diagram of the thyristor-to-PWM LED dimming circuit of this utility model.

[0019] Figure 3 This is a circuit diagram of the power module of this utility model;

[0020] Figure 4 This is a circuit diagram of the boost circuit of this utility model;

[0021] Figure 5 This is a circuit diagram of the flyback buck circuit of this utility model;

[0022] Figure 6 This is a circuit diagram of the thyristor detection circuit of this utility model;

[0023] Figure 7 The circuit diagrams are for the thyristor dimming-to-analog dimming circuit and the analog dimming-to-PWM dimming circuit of this utility model.

[0024] Figure 8 This is a circuit diagram of the output rectifier circuit of this utility model;

[0025] Figure 9 This is a circuit diagram of the thyristor-to-PWM LED dimming circuit of this utility model.

[0026] In the attached diagram: 1-Power supply module, 2-Boost circuit, 3-Flyback buck circuit, 4-SCR detection circuit, 5-SCR dimming to analog dimming circuit, 6-Analog dimming to PWM dimming circuit, 7-Auxiliary power supply circuit, 8-Output rectifier circuit.

[0027] The realization of the purpose, functional features and advantages of this utility model will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0028] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present utility model.

[0029] It should be noted that if the embodiments of this utility model involve directional indicators, such as up, down, left, right, front, back, etc., the directional indicators are only used to explain the relative positional relationship and movement of the components in a specific posture. If the specific posture changes, the directional indicators will also change accordingly.

[0030] Furthermore, if the embodiments of this utility model involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this utility model.

[0031] The main purpose of this invention is to solve the technical problems of poor compatibility between thyristor dimming and PWM dimming, large circuit size and low efficiency in the prior art.

[0032] like Figures 1 to 9 As shown, this utility model proposes an LED dimming circuit that converts a silicon controlled rectifier (SCR) to a PWM converter, including a power supply module 1, a boost circuit 2, a flyback buck circuit 3, a SCR detection circuit 4, a SCR dimming-to-analog dimming circuit 5, an analog dimming-to-PWM dimming circuit 6, and an auxiliary power supply circuit 7. The input terminal of power module 1 is connected to a thyristor dimmer to convert phase-cut AC power into primary DC voltage. The input terminal of boost circuit 2 is connected to the output terminal of power module 1 to boost the primary DC voltage into high-voltage DC power. The input terminal of flyback buck circuit 3 is connected to the output terminal of boost circuit 2 to convert the high-voltage DC power into a first DC power to power the LED load. The input terminal of thyristor detection circuit 4 is connected to the AC side of power module 1 to extract the thyristor conduction angle signal and generate a square wave signal. The input terminal of thyristor dimming to analog dimming circuit 5 is connected to the output terminal of thyristor detection circuit 4 to convert the square wave signal into an analog voltage signal. The input terminal of analog dimming to PWM dimming circuit 6 is connected to the output terminal of thyristor dimming to analog dimming circuit 5, and the output terminal is connected to the PWM control terminal of flyback buck circuit 3 to convert the analog voltage signal into a PWM control signal. The input terminal of auxiliary power supply circuit 7 is connected to the output terminal of boost circuit 2 to convert the high-voltage DC power into a second DC power to power the control module in the circuit.

[0033] For details, see Figure 2As shown, in this embodiment, the input terminal of power module 1 is connected to a thyristor dimmer. Power module 1 includes a rectifier bridge BD1, an EMI filter circuit, and an active damping circuit. The L line of the input terminal is connected to the AC input terminal of rectifier bridge BD1 through fuse F1, and the N line is directly connected to the other end of rectifier bridge BD1. The EMI filter circuit includes common-mode inductors L3 and L2 and X capacitor CX1. Its core function is to suppress high-frequency differential-mode and common-mode noise in the power grid and protect the subsequent rectifier bridge BD1 and active damping circuit from interference. The output terminal of rectifier bridge BD1 is connected to an active damping circuit composed of a fourth diode ZD3 and a fourth MOSFET Q1 to suppress peak current and prevent the thyristor dimmer from being falsely triggered. The input of boost circuit 2 is connected to the output of power module 1, used to boost the primary DC voltage to a high-voltage DC of 400V. Boost circuit 2 uses APFC control chip U1 to achieve active power factor correction, specifically including a second inductor L1, a third MOSFET Q2, a third diode D02, a ferrite bead DB, and a fourth capacitor CE1. The drive terminal GATE of APFC control chip U1 drives the gate of the third MOSFET Q2 through resistor R07. The drain of the third MOSFET Q2 is connected to one end of the second inductor L1, and the source is grounded. The second end of the ferrite bead DB outputs 400V high-voltage DC, which is fed back to the fourth input terminal FB of APFC control chip U1 through a resistor voltage divider network to achieve closed-loop regulation. The input of flyback buck circuit 3 is connected to the output of boost circuit 2, used to convert the high-voltage DC to a primary DC to power the LED load. The flyback buck circuit 3 includes a dimming control chip U2, a first transformer T2 (including a primary winding T2A, a secondary winding T2B, and an auxiliary winding T2C), a second MOSFET Q3, and an output rectifier circuit. The driving terminal GATE of the dimming control chip U2 drives the gate of the second MOSFET Q3 through a resistor R26. The drain of the second MOSFET Q3 is connected to one end of the primary winding of the first transformer T2A, and the source is grounded. The output terminal of the secondary winding of the first transformer T2B is rectified and filtered by two diodes D1 and a third capacitor CE2 to supply power to the LED load. The input terminal of the thyristor detection circuit 4 is connected to the AC side of the power supply module 1, including a voltage reference chip U7, a first transistor Q4, a first MOSFET Q5, and an optocoupler U6. The reference terminal of the voltage reference chip U7 detects the thyristor conduction angle signal through resistors R29-R31 and diodes BD2 / BD3. The output terminal drives the base of the first transistor Q4. The collector of the first transistor Q4 is connected to the gate of the first MOSFET Q5. The drain of the first MOSFET Q5 is connected to the input terminal of the optocoupler U6. The output terminal of the optocoupler U6 generates an isolated square wave signal.The input of the analog dimming-to-PWM dimming circuit 6 is connected to the output of the thyristor dimming-to-analog dimming circuit 5, and the output is connected to the PWM control terminal of the flyback buck circuit 3. This circuit uses a dimming converter chip U3, whose second input terminal DIM receives the analog voltage signal and converts it into a PWM signal through an internal algorithm. The first output terminal OUT of the dimming converter chip U3 outputs the PWM signal to the second input terminal PWM of the dimming control chip U2, and the current of the LED load is controlled by adjusting the PWM duty cycle. The auxiliary power supply circuit 7 includes a BP2525B chip U4, which constructs a DC-DC conversion structure through inductor L5, capacitor EC6, diode D11, etc., to convert the 400V high-voltage DC output from the boost circuit into a stable 24V DC voltage, providing reliable power supply for the chips in the entire control system and ensuring the normal operation of each module. Two independent paths are formed between the modules: the main power path realizes the energy conversion from AC to DC to high-voltage DC to isolated DC; the control signal path completes the signal conversion from phase angle to square wave to analog to PWM. The two paths are isolated by opto-isolators to ensure the safety and reliability of the system.

[0034] The working process is as follows: AC power is input to power module 1 after phase cutting by a thyristor dimmer. The L line is connected to rectifier bridge BD1 through fuse F1, and the N line is directly connected to the other end of BD1. Common mode inductors L3 / L2 and capacitor X CX1 filter out high-frequency noise. The pulsating DC output from rectifier bridge BD1 is suppressed by the fourth diode ZD3 and the fourth MOSFET Q1 to form the primary DC voltage. In boost circuit 2, APFC control chip U1 controls the third MOSFET Q2 and the second inductor L1 to work together to boost the primary DC voltage through the driver terminal GATE. The 400V high-voltage DC power is filtered by the fourth capacitor CE1 and then input to the flyback buck circuit. The dimming control chip U2 of the flyback buck circuit 3 controls the second MOSFET Q3 to drive the first transformer T2 through the driver terminal GATE. The secondary winding T2B is rectified and filtered by the two diodes D1 and the third capacitor CE2 to output DC power to drive the LED load. In the thyristor detection circuit 4, the diodes BD2 / BD3 and resistors R29-R31 divide the voltage to extract the conduction angle signal. The voltage reference chip U7 outputs a square wave signal, which is amplified by the first transistor Q4 and then drives the first MOSFET. The first MOSFET Q5 controls the optocoupler isolator U6 to generate an isolated square wave signal. The thyristor-controlled dimming-to-analog dimming circuit 5 converts the square wave signal output from optocoupler U6 into a smooth analog voltage signal through a filter network composed of resistors R53-R54 and capacitors C16-C17, which is then transmitted to the base of the second transistor Q7. The second transistor Q7, together with resistor R56 and capacitor C17, forms a buffer circuit, outputting a 0-10V analog voltage to the analog dimming-to-PWM dimming circuit 6. The dimming conversion chip U3 of the analog dimming-to-PWM dimming circuit 6 converts the square wave signal... The signal is converted into a PWM signal, which adjusts the LED current through the PWM pin of the dimming control chip U2; the BP2525B chip U4 in the auxiliary power supply circuit 7 converts the 400V high voltage into 24V DC power to power the APFC control chip U1, the dimming conversion chip U3, the first transistor Q4, and the optocoupler U6; the main power path completes the energy conversion from AC to DC to high voltage DC to isolated DC, and the control signal path achieves phase angle-square wave-analog-PWM isolation conversion through optocoupler isolation. The dual paths work together to achieve efficient dimming and low ripple output.

[0035] Understandably, in this embodiment, the phase AC power cut by the SCR dimmer is converted into a primary DC voltage by the power module 1, which is then boosted by the boost circuit 2 and input to the flyback buck circuit 3 to form the main power path. The SCR detection circuit 4 extracts the conduction angle signal from the AC side of the power module 1, which is then converted into a PWM control signal through the SCR dimming-to-analog dimming circuit 5 and the analog dimming-to-PWM dimming circuit 6, forming an isolated control signal path. The two paths operate independently and are isolated by optocouplers to block interference, which can adapt to the SCR dimmer and achieve full-range dimming from 1% to 100%. The boost circuit 2 uses an APFC control chip to achieve power factor correction. The positive voltage boost circuit 3 and the flyback buck circuit 4 precisely regulate the LED current through PWM control. The two circuits work together to reduce output ripple. The main power path can suppress flicker without large-capacity electrolytic capacitors, thus improving conversion efficiency. The auxiliary power supply circuit 7 extracts a stable low-voltage power supply from the high-voltage side of the boost circuit 2 to provide isolated power to the control module and prevent signal path interference from the main power. Through the coordinated work of the boost circuit and the flyback buck circuit, the output rectifier circuit only needs small-capacity electrolytic capacitors for filtering, which can effectively improve conversion efficiency and reduce losses. Compared with the traditional single-stage flyback flicker-eliminating IC circuit solution, the two-stage solution is more cost-effective, more efficient, and smaller in size.

[0036] Preferably, the thyristor detection circuit 4 includes a voltage reference chip, a first transistor, a first MOSFET, and an optocoupler; the reference terminal of the voltage reference chip is connected to the AC input terminal of the power supply module 1 to detect the thyristor conduction angle signal and generate a square wave signal at the output terminal; the emitter of the first transistor is connected to the output terminal of the auxiliary power supply circuit 7, and the base is connected to the output terminal of the voltage reference chip to amplify the square wave signal; the gate of the first MOSFET is connected to the collector of the first transistor, the drain is connected to the output terminal of the auxiliary power supply circuit 7 and the first input terminal of the optocoupler, and the source and the second input terminal of the optocoupler are grounded; the output terminal of the optocoupler generates an isolated square wave signal.

[0037] For details, see Figure 2 and Figure 6As shown, in this embodiment, the thyristor detection circuit 4 includes a voltage reference chip U7, a first transistor Q4, a first MOSFET Q5, and an optocoupler U6; in this embodiment, the voltage reference chip U7 is a TL431, the optocoupler U6 is an 817C, the first transistor Q4 is a 2N8550, and the first MOSFET Q5 is a 2N7002. Power module 1 includes a rectifier bridge BD1. The first AC input terminal of rectifier bridge BD1 is connected to the anode of diode BD2, and the second AC input terminal of rectifier bridge BD1 is connected to the anode of diode BD3. The cathodes of diodes BD2 and BD3 are shared by the first terminal of resistor R29. The second terminal of resistor R29 is connected to the first terminal of resistor R31 via resistor R30. The second terminal of resistor R31 is connected to the first terminals of resistors R32 and R35, and the reference terminal of voltage reference chip U7. The anode of voltage reference chip U7 is grounded, and the cathode is connected to the second terminal of resistor R34. The first terminal of resistor R34 is connected to the base of the first transistor Q4, and a resistor is connected between the emitter and base of the first transistor Q4. R33; The collector of the first transistor Q4 is connected to the positive terminal of diode D08 and the first end of resistor R36, and the negative terminal of D08 is connected to the first end of R35; the second end of R36 is connected to the first end of resistor R37 and the gate of the first MOSFET Q5; the source of the first MOSFET Q5 is grounded, and the drain is connected to the first input terminal (diode positive terminal) of optocoupler U6 and the second end of resistor R38, and the second input terminal (diode negative terminal) of optocoupler U6 is grounded; the emitter of the first transistor Q4, the first end of resistor R38, the first end of electrolytic capacitor CE4, and the first end of capacitor C23 are all connected to the 24V power supply provided by the output terminal of auxiliary power supply circuit 7, and the second end of electrolytic capacitor CE4 and capacitor C23 are grounded.

[0038] The working process is as follows: The AC power supply, after phase cutting by the thyristor dimmer, is input to the AC side of the rectifier bridge BD1; diodes BD2 and BD3 are respectively connected to the two AC input terminals of BD1, and the negative terminals of BD2 and BD3 are connected to the first terminal of resistor R29, forming a conduction angle signal extraction node; resistors R29-R31 form a voltage divider network, attenuating the thyristor conduction angle signal before inputting it to the reference terminal of the voltage reference chip U7; the voltage reference chip U7 compares the reference terminal voltage with the internal reference and outputs a square wave signal corresponding to the conduction angle at its cathode; the square wave signal is transmitted to the first transistor Q4 via resistor R34. The base and emitter of the first transistor Q4 are connected to a 24V auxiliary power supply. The base-emitter resistor R33 provides bias current. The collector outputs an amplified square wave signal, which drives the gate of the first MOSFET Q5. When the first MOSFET Q5 is turned on, it pulls down the input current of the optocoupler U6, causing the optocoupler U6 to generate an isolated square wave signal at its output. Electrolytic capacitor CE4 and capacitor C23 filter the 24V power supply to suppress high-frequency noise. Finally, the isolated square wave signal output by the optocoupler U6 is transmitted to the thyristor dimming-to-analog dimming circuit 5, completing the accurate extraction and isolated transmission of the thyristor dimming signal.

[0039] Understandably, in this embodiment, the voltage reference chip U7 accurately acquires the thyristor conduction angle signal through the resistor divider network R29-R31. Combined with the amplification effect of the first transistor Q4, the signal distortion caused by the impedance difference of the dimmer can be effectively eliminated. The optocoupler U6 isolates the thyristor detection signal from the subsequent control circuit, which can block the conduction of common-mode noise and ensure stable transmission of the dimming signal under high voltage. The optocoupler U6 is driven by the first MOSFET Q5, which has low operating current and fast response time, effectively avoiding the high power consumption and delay problems of traditional operational amplifier solutions. Those skilled in the art can make equivalent improvements based on the above design, such as: replacing the voltage reference chip U7 with a programmable reference source of the same type as LMV431 or AZ431; or replacing the first MOSFET Q5 with a low-voltage logic level MOSFET such as AO3400 or DMG2302; or adjusting the resistor divider network to adapt to the trigger current requirements of different dimmers; or adjusting the capacitance value of the filter capacitor C23 to suppress high-frequency noise from the 24V power supply; or replacing the optocoupler isolator U6 with a digital isolation chip or a magnetic isolation module to improve signal transmission rate and lifespan.

[0040] Preferably, the analog dimming to PWM dimming circuit 6 includes a dimming conversion chip; the first input terminal of the dimming conversion chip is connected to the output terminal of the auxiliary power supply circuit 7, and the second input terminal is connected to the output terminal of the thyristor dimming to analog dimming circuit 5; the first output terminal of the dimming conversion chip is connected to the PWM control terminal of the flyback buck circuit 3, which is used to convert the analog voltage signal into a PWM control signal and adjust the LED load current.

[0041] For details, see Figure 2 and Figure 7 As shown, in this embodiment, the analog dimming to PWM dimming circuit 6 includes a dimming conversion chip U3, model BP5001; the first input terminal HV of the dimming conversion chip U3 is connected to the 24V power supply provided by the output terminal of the auxiliary power supply circuit 7, the second input terminal DIM is connected to the output terminal of the thyristor dimming to analog dimming circuit 5, and the GND terminal is grounded; the first output terminal OUT of the dimming conversion chip U3 is connected to the PWM terminal of the dimming control chip U2 of the flyback buck circuit 3, and is also connected to the second terminal of resistor R51, the first terminal of capacitor C21 and the first terminal of resistor R48; the second output terminal VCC of the dimming conversion chip U3 outputs 13V power supply; the second terminal of capacitor C21 and the second terminal of resistor R48 are grounded.

[0042] Understandably, this embodiment receives a 0-10V analog voltage signal through the second input terminal DIM of the dimming converter chip U3, achieving a linear conversion from analog signal to PWM signal, thus avoiding dimming flicker or nonlinearity problems caused by signal distortion in traditional solutions. Simultaneously, the first input terminal HV of the dimming converter chip U3 is directly connected to the 24V power supply provided by the auxiliary power supply circuit 7. This isolated power supply design blocks high-frequency noise interference from the main power circuit, ensuring the stability of the PWM signal generation process. Those skilled in the art can make equivalent improvements based on the above design, such as replacing the dimming converter chip U3 with an LED driver IC that supports analog-to-PWM conversion, such as SN3350 or LT3797; adjusting the parameters of the resistors and capacitors according to the application scenario; or adding a Zener diode or LDO chip to the 24V power supply path to further suppress power supply noise.

[0043] Preferably, the thyristor-controlled dimming to analog dimming circuit 5 includes a second transistor, a first resistor, and a filter and rectifier circuit; the first output terminal of the optocoupler is connected to the second output terminal of the dimming conversion chip through the first resistor; the second output terminal of the optocoupler is grounded, and the first output terminal is connected to the base of the second transistor through the filter and rectifier circuit; the collector of the second transistor is connected to the second output terminal of the dimming conversion chip, and the emitter is connected to the second input terminal of the dimming conversion chip.

[0044] For details, see Figure 2 and Figure 7As shown, in this embodiment, the thyristor-controlled dimming to analog dimming circuit 5 includes a second transistor Q7, a first resistor R53, and a filter and rectifier circuit. The filter and rectifier circuit includes a resistor R54, a capacitor C16, a diode D09, a diode D10, and a diode D13. The first end of the first resistor R53 is connected to the second output terminal VCC of the dimming converter chip U3 to obtain 13V power supply, and the second end is connected to the first end of the resistor R54 and the first output terminal of the optocoupler U6. The second output terminal of the optocoupler U6 is grounded. The second end of the resistor R54 is connected to the anode of the diode D09 and the first end of the capacitor C16. The second end of the capacitor C16 is grounded. The cathode of the diode D09 is connected to the anode of the diode D10, the cathode of the diode D10 is connected to the anode of the diode D13, and the cathode of the diode D13 is connected to the base of the second transistor Q7. The emitter of the second transistor Q7 is connected to the first end of the resistor R56, the first end of the capacitor C17, and the second input terminal DIM of the dimming converter chip U3. The second end of the resistor R56 and the second end of the capacitor C17 are grounded.

[0045] Understandably, in this embodiment, the RC filter network composed of resistor R54 and capacitor C16 filters out the high-frequency noise of the square wave signal output by optocoupler U6, generating a smooth DC signal; the series rectification of diodes D09-D10-D13 eliminates the negative half-cycle interference signal, ensuring that the voltage at the base of the second transistor Q7 is a unidirectional pulsating DC; the second transistor Q7, as an emitter follower, provides low output impedance, ensuring that the analog signal is stably transmitted to the DIM pin of the dimming converter chip U3, avoiding signal distortion caused by load fluctuations. Those skilled in the art can make equivalent improvements based on the above design, such as: replacing diodes D09-D10-D13 with a single high-voltage fast recovery diode or an integrated level shifter chip to simplify the circuit structure; or adjusting the parameter range of resistor R54 and capacitor C16 to adapt to input signals of different frequencies; replacing the second transistor Q7 with a general-purpose NPN transistor and adjusting the base resistor accordingly; connecting an adjustable resistor in series between diode D13 and the second transistor Q7 to achieve manual calibration of the analog signal amplitude; adding a parallel Zener diode to limit the peak voltage of the signal to protect the input port of the dimming converter chip; or using a digital isolator to replace optocoupler U6 to improve the signal transmission rate and anti-interference capability.

[0046] Preferably, the flyback buck circuit 3 includes a dimming control chip, a first transformer, and a second MOSFET; the first input terminal of the dimming control chip is connected to the output terminal of the boost circuit 2, the second input terminal is connected to the output terminal of the analog dimming to PWM dimming circuit 6, and the driving terminal is connected to the gate of the second MOSFET; the first end of the primary winding of the first transformer is connected to the output terminal of the boost circuit 2, and the second end is connected to the drain of the second MOSFET; the source of the second MOSFET is grounded.

[0047] For details, see Figure 2 and Figure 5As shown, in this embodiment, the flyback buck circuit 3 includes a dimming control chip U2, a first transformer T2, and a second MOSFET Q3; the dimming control chip U2 is a BP3179D, and the second MOSFET Q3 is a 70R450P; the first terminal of the primary winding T2A of the first transformer T2 is connected to the output terminal of the boost circuit 2, and the second terminal is connected to the drain of the second MOSFET Q3, while the source of the second MOSFET Q3 is grounded; the first input terminal VCC of the dimming control chip U3 is connected to the output terminal of the boost circuit 2 through a voltage divider resistor network. In this embodiment, the voltage divider... The resistor network includes resistors R47, R52, R46, R45, R50, and R48. The second input terminal (PWM pin) of the dimming control chip U2 is connected to the output terminal of the analog dimming to PWM dimming circuit 6, i.e., the OUT pin of the dimming conversion chip U3. The driving terminal (GATE pin) of the dimming control chip U2 is connected to the gate of the second MOSFET Q3. The switching frequency and duty cycle of the second MOSFET Q3 are controlled according to the PWM signal, thereby precisely adjusting the energy transmission efficiency of the first transformer T2 and realizing the dimming control of the LED load current.

[0048] Understandably, in this embodiment, the dimming control chip U2 directly outputs a PWM signal through its GATE pin to drive the gate of the second MOSFET Q3. Based on the PWM command from the analog dimming-to-PWM dimming circuit 6, the switching duty cycle of the second MOSFET Q3 is dynamically adjusted, achieving precise control of the energy transfer efficiency of the first transformer T2. This allows for stepless adjustment of the LED load current, reducing dimming linearity errors. Simultaneously, the combination of the flyback topology and the low on-resistance characteristics of the high-voltage MOSFET improves the overall conversion efficiency and eliminates the need for complex external sampling circuits, significantly simplifying system design. Those skilled in the art can make equivalent improvements based on the above design, such as replacing the second MOSFET Q3 with other low on-resistance MOSFETs to reduce switching losses; adjusting the resistance value of the external resistor at the GATE pin of the dimming control chip U2 to optimize switching speed; using a first transformer T2 with different packages or power ratings to adapt to higher / lower voltage LED loads; adding an RC buffer circuit between the drain of the second MOSFET Q3 and the first transformer T2A to suppress voltage spikes; changing the dimming control chip model and adapting its drive logic level, etc.

[0049] Preferably, the flyback buck circuit 3 further includes a third transistor, a first diode, and a second diode; the anode of the first diode is connected to the first end of the auxiliary winding of the first transformer, and the second end of the auxiliary winding of the first transformer is grounded; the collector of the third transistor is connected to the cathode of the first diode, the emitter is connected to the first input terminal of the dimming control chip, and the base is connected to the anode of the second diode; the cathode of the second diode is grounded.

[0050] For details, see Figure 2 and Figure 5 As shown, in this embodiment, the flyback buck circuit 3 further includes a third transistor Q8, a first diode D05, and a second diode ZD1; the third transistor Q8 is an S8050, and the second diode ZD1 is an 18V Zener diode; the anode of the first diode D05 is connected to the first terminal of the auxiliary winding T2C of the first transformer T2, and the second terminal of the auxiliary winding T2C of the first transformer T2 is grounded; the collector of the third transistor Q8 is connected to the cathode of the first diode D05, the emitter is connected to the first input terminal VCC of the dimming control chip U2, and the base is connected to the anode of the second diode ZD1; the cathode of the second diode ZD1 is grounded.

[0051] Understandably, in this embodiment, the induced voltage of the auxiliary winding T2C of the first transformer T2 is rectified by the first diode D05, and the third transistor Q8, acting as an emitter follower, outputs a low-impedance VCC voltage to the dimming control chip U2. Combined with the second diode ZD1 clamping the base voltage, this ensures that the operating voltage of the dimming control chip U2 remains stable within the required range, preventing chip damage due to input fluctuations. This embodiment utilizes the flyback transformer's auxiliary winding for self-powering, eliminating the need for an additional independent power supply module and reducing the number of components and cost. Those skilled in the art can make equivalent improvements based on the above design, such as replacing the third transistor Q8 with other NPN transistors and adjusting the base resistor R18 to adapt to different amplification factors; or using a second diode ZD1 with different voltage regulation values ​​to match the voltage withstand requirements of the dimming control chip U2; or adding a current-limiting resistor between the cathode of the first diode D05 and the collector of the third transistor Q8 to optimize rectification efficiency; or using a low-dropout linear regulator (LDO) to replace the combination of the second diode ZD1 and the third transistor Q8 to further improve power supply accuracy.

[0052] Preferably, the flyback buck circuit 3 further includes a voltage detection circuit and a current detection circuit; the voltage detection circuit includes a second resistor, a third resistor, and a first capacitor, the first end of the second resistor is connected to the first end of the auxiliary winding of the first transformer, the second end of the second resistor, the first end of the third resistor, and the first end of the capacitor are all connected to the third input terminal of the dimming control chip, and the second end of the third resistor and the second end of the first capacitor are grounded; the current detection circuit includes a fourth resistor, a fifth resistor, and a second capacitor, the first end of the fourth resistor and the first end of the second capacitor are all connected to the fourth input terminal of the dimming control chip, the second end of the fourth resistor and the first end of the fifth resistor are all connected to the source of the second MOSFET, and the second end of the fifth resistor and the second end of the second capacitor are grounded.

[0053] For details, see Figure 2 and Figure 5As shown, in this embodiment, the voltage detection circuit includes a second resistor R16, a third resistor R17, and a first capacitor C07. The first end of the second resistor R16 is connected to the first end of the auxiliary winding T2C of the first transformer T2. The second end of the second resistor R16, the first end of the third resistor R17, and the first end of the capacitor are all connected to the third input terminal FB of the dimming control chip U2. The second end of the third resistor R17 and the second end of the first capacitor are grounded. The current detection circuit includes a fourth resistor R1, a fifth resistor RS2, and a second capacitor C09. The first end of the fourth resistor R1 and the first end of the second capacitor C09 are all connected to the fourth input terminal CS of the dimming control chip U2. The second end of the fourth resistor R1 and the first end of the fifth resistor RS2 are all connected to the source of the second MOS transistor. The second end of the fifth resistor RS2 and the second end of the second capacitor C09 are grounded.

[0054] Understandably, this embodiment effectively reduces output voltage and current errors through the coordinated feedback design of the voltage detection circuit and the current detection circuit. The voltage detection circuit samples the voltage of the auxiliary winding T2C of the first transformer T2 through a voltage divider between the second resistor R16 and the third resistor R17. After being filtered by the first capacitor C07, the voltage is input to the third input terminal FB of the dimming control chip U2. Combined with the internal reference source, closed-loop voltage regulation control is achieved, reducing output voltage errors. The current detection circuit detects the source current of the second MOSFET Q3 in real time through the fifth resistor RS2. After being filtered by the fourth resistor R1 and the second capacitor C09, the current is input to the fourth input terminal CS of the dimming control chip U2, dynamically adjusting the PWM duty cycle and reducing output current errors. Those skilled in the art can make equivalent improvements based on the above design, such as replacing the voltage divider resistors R16 / R17 with adjustable resistors or digital potentiometers to adapt to different output voltage requirements; or adjusting the capacitance range of the first capacitor C07 and the second capacitor C09 to optimize the high-frequency noise suppression effect; or using a thin-film resistor or a surface-mount alloy resistor to replace the fifth resistor RS2 to improve the current sampling accuracy; or using an integrated current sensing amplifier in conjunction with the dimming control chip U2 to simplify the peripheral circuit; or replacing the fourth resistor R1 with an RC series network to enhance the high-frequency filtering performance.

[0055] Preferably, it also includes an output rectifier circuit 8, which includes two diodes, a first inductor, a primary filter circuit, and a secondary filter circuit. The first end of the two diodes is connected to the output end of the flyback buck circuit 3, and the second end of the two diodes is connected to the first input end of the first inductor. The second input end of the first inductor is grounded, and its output end is used to power the LED load. The primary filter circuit is connected between the first and second ends of the two diodes, and the secondary filter circuit is connected between the second end of the two diodes and ground.

[0056] For details, see Figure 2 and Figure 9As shown, in this embodiment, the output rectifier circuit 8 includes dual diodes D1, a first inductor L4, a primary filter circuit, and a secondary filter circuit. The first end of the dual diodes D1 is connected to the output end of the flyback buck circuit 3, i.e., the first output end of the secondary winding T2B of the first transformer T2. The second end of the dual diodes D1 is connected to the first input end of the first inductor L4. The second input end of the first inductor L4 is grounded, and its output end is used to power the LED load. The primary filter circuit includes a capacitor C13, a resistor R39, and a resistor R40. The first end of the capacitor C13 is connected to the first end of the dual diodes D1, and the second end of the capacitor C13 is connected to the second end of the dual diodes D1 through the parallel resistors R39 and R40. The secondary filter circuit includes a capacitor CE2 and a resistor R41, which are connected in parallel between the second end of the dual diodes D1 and ground.

[0057] Understandably, in this embodiment, the high-frequency AC output of the secondary winding T2B of the first transformer T2 is rectified by dual diodes D1, combined with the first inductor L4 to suppress current surges, the primary filter circuit filters out high-frequency switching noise, and the secondary filter circuit further smooths the DC output, resulting in a smaller overall output ripple voltage and meeting the requirement of flicker-free LEDs. In the primary filter circuit, the parallel resistors R39 and R40 provide a voltage equalization path for the two arms of the dual diodes D1, avoiding voltage imbalance caused by parasitic parameters, while also sharing heat loss and effectively reducing diode temperature rise. The dual diodes D1 integrate a dual-chip structure to replace discrete diodes, reducing PCB area. The secondary filter capacitor CE2 is connected in parallel with the discharge resistor R41 to avoid the accumulation of residual charge in the capacitor, eliminating the need for an independent discharge circuit and reducing costs. Those skilled in the art can make equivalent improvements based on the above design, such as replacing the dual diodes D1 with synchronous rectifier MOSFETs to improve efficiency; or adjusting the capacitance of the primary filter capacitor C13 and the resistance of resistors R39 / R40 to adapt to different switching frequencies; or using a π-type filter to replace the secondary filter circuit CE2 to further reduce ripple; or replacing the bleed resistor R41 with an NTC thermistor to achieve temperature-adaptive discharge; or using a low-ESR electrolytic capacitor to replace CE2 to improve high-frequency characteristics.

[0058] Preferably, the boost circuit 2 includes an APFC control chip, a second inductor, a third MOSFET, a fourth capacitor, and a third diode; the first terminal of the second inductor, the anode of the third diode, and the drain of the third MOSFET are all connected to the output terminal of the power module 1; the second terminal of the second inductor and the cathode of the third diode are all connected to the first terminal of the fourth capacitor; the first input terminal of the APFC control chip is connected to the output terminal of the auxiliary power supply circuit 7, and the driving terminal is connected to the gate of the third MOSFET; the source of the third MOSFET is grounded.

[0059] For details, see Figure 2 and Figure 4As shown, in this embodiment, the boost circuit 2 includes an APFC control chip U1, a second inductor L1, a third MOSFET Q2, a fourth capacitor CE1, and a third diode D02; the APFC control chip U1 is a BP2628, and the third MOSFET Q2 is a 12N65; the first terminal of the second inductor L1, the anode of the third diode D02, and the drain of the third MOSFET Q2 are all connected to the output terminal of the power module 1; the second terminal of the second inductor L1 and the cathode of the third diode D02 are all connected to the first terminal of the fourth capacitor CE1; the first input terminal VCC of the APFC control chip U1 is connected to the output terminal of the auxiliary power supply circuit 7 to obtain 24V power supply, and the driving terminal GATE is connected to the gate of the third MOSFET Q2; the source of the third MOSFET Q2 is grounded. The working process is as follows: After rectification by rectifier bridge BD1, AC power outputs pulsating DC power to the second inductor L1; APFC control chip U1 outputs a signal through the GATE pin to drive the third MOSFET Q2 to periodically turn on and off. When the third MOSFET Q2 is on, the second inductor L1 stores energy, and the current flows through the third MOSFET Q2 to ground; when the third MOSFET Q2 is off, the second inductor L1 releases energy, which, after being superimposed with the input voltage, charges the fourth capacitor CE1 through the third diode D02, generating a 400V high-voltage DC power; the ferrite bead DB is used to suppress high-frequency noise, and resistors R11-R14 form a voltage divider network to feed the output voltage back to the FB pin of APFC control chip U1, and the closed-loop adjustment of the PWM duty cycle is used to stabilize the output voltage; at the same time, the ZCD pin of APFC control chip U1 detects the zero-point current of the second inductor L1 through resistor R06 to optimize the power factor; after filtering by the fourth capacitor CE1, a smooth high-voltage DC power is output to the flyback buck circuit 3 to complete the boost and power factor correction.

[0060] Understandably, in this embodiment, the APFC control chip U1 detects the zero-point current of the second inductor L1 through the ZCD pin and dynamically adjusts the switching timing of the third MOSFET Q2 to make the input current waveform follow the input voltage. The low on-resistance of the third MOSFET Q2 and the fast recovery characteristics of the third diode D02 work together to reduce switching losses and improve the overall conversion efficiency. The voltage divider resistor network R11-R14 forms a closed-loop feedback circuit, which samples the 400V high voltage output in real time and feeds it back to the FB pin of the APFC control chip U1. Combined with the energy storage and filtering of the fourth capacitor CE1, the output voltage ripple can be effectively reduced and adapted to wide load fluctuations. Those skilled in the art can make equivalent improvements based on the above design, such as replacing the APFC control chip U1 with other control chips and adjusting the resistance value of the detection resistor R06 around the ZCD pin; or replacing the third MOSFET Q2 with a SiC MOSFET to further increase the switching frequency to above 200kHz; or replacing the third diode D02 with a synchronous rectifier MOSFET and configuring a drive circuit to reduce conduction losses; or adjusting the resistance range of the voltage divider resistors R11-R14 to adapt to different output voltage requirements; or replacing the fourth capacitor CE1 with a low ESR electrolytic capacitor or a film capacitor to optimize high-frequency filtering performance; or adding an RC snubber circuit between the second inductor L1 and the third MOSFET Q2 to suppress voltage spikes.

[0061] Preferably, the power module 1 includes a rectifier bridge, a fourth diode, a sixth resistor, and a fourth MOSFET; the first DC output terminal of the rectifier bridge is connected to the gate of the fourth MOSFET and the cathode of the fourth diode, the second DC output terminal of the rectifier bridge is connected to the anode of the fourth diode, the first terminal of the sixth resistor, and the source of the fourth MOSFET, and the drain of the fourth MOSFET and the second terminal of the sixth resistor are grounded.

[0062] For details, see Figure 2 and Figure 3As shown, in this embodiment, the AC input L line is connected to the first input terminal of the common-mode inductor L3 via fuse F1, and the N line is directly connected to the second input terminal of the common-mode inductor L3; the first and second output terminals of the common-mode inductor L3 are respectively connected to the first and second input terminals of the common-mode inductor L2; the first output terminal of the common-mode inductor L2 is connected to the first AC input terminal of the rectifier bridge BD1, and the second output terminal is connected to the second AC input terminal of the rectifier bridge BD1; the first DC output terminal of the rectifier bridge BD1 is connected to the second terminal of resistor R61, the first terminal of resistor R61 is connected to the second terminal of resistor R62, and the first terminal of resistor R62 is connected to the second terminal of the Zener diode Z. The cathode of D3, the first terminal of resistor R04, and the first terminal of capacitor C01 are all connected to the gate of the fourth MOSFET Q1; the second terminal of the DC output of rectifier bridge BD1 is connected to the anode of Zener diode ZD3, the second terminal of resistor R04, the second terminal of capacitor C01, and the source of the fourth MOSFET Q1; the drain of the fourth MOSFET Q1 is grounded, and resistor R1 is connected between the drain and the source; a varistor VAR1 is connected between the first and second input terminals of common-mode inductor L3, and capacitor CX1 is connected between the first and second input terminals of common-mode inductor L2; common-mode inductors L3 and L2 constitute a two-stage EMI filter to suppress high-frequency common-mode and differential-mode noise.

[0063] Understandably, this embodiment effectively blocks high-frequency noise from the power grid from being transmitted to subsequent circuits through a two-stage EMI filtering design using common-mode inductors L3 / L2 and capacitor CX1. The pulsating DC output from rectifier bridge BD1 is controlled by an active damping circuit composed of the fourth MOSFET Q1, Zener diode ZD3, and resistor network R61 / R62 / R04 to suppress surge current and voltage spikes when the thyristor dimmer is turned on, preventing overvoltage damage to the rectifier bridge. Resistor R04 and capacitor C01 form a gate soft-start circuit, which can smooth the conduction slope of the fourth MOSFET Q1 and ensure stable and reliable damping operation. The system is compatible with wide voltage input, has low standby power consumption, and does not require an additional NTC thermistor, thus reducing cost and size. Those skilled in the art can make equivalent improvements based on the above design, such as replacing the varistor VAR1 with a gas discharge tube to enhance overvoltage protection capability; or adjusting the resistance range of resistors R61 / R62 or the capacitance value of capacitor C01 to adapt to different surge current levels; or using a TVS diode to replace the Zener diode ZD3 to improve transient suppression performance; or adding an RC snubber circuit between the drain of the fourth MOSFET Q1 and ground to further suppress turn-off voltage spikes; or replacing the common-mode inductors L3 / L2 with an integrated filter module to reduce PCB area.

[0064] This invention proposes a thyristor-to-PWM LED dimming circuit. Power module 1 converts the phase AC power cut by the thyristor dimmer into a primary DC voltage, which is then boosted by boost circuit 2 and input to flyback buck circuit 3, forming the main power path. The thyristor detection circuit 4 extracts the conduction angle signal from the AC side of power module 1, which is then converted into a PWM control signal through thyristor-to-analog dimming circuit 5 and analog dimming-to-PWM dimming circuit 6, forming an isolated control signal path. The two paths operate independently and are isolated by optocouplers to block interference, allowing for compatibility with thyristor dimmers and achieving full-range dimming from 1% to 100%. Boost circuit 2 is controlled by an APFC chip. Achieving power factor correction and high-voltage boost, the flyback buck circuit 3 precisely adjusts the LED current through PWM control. The two-stage circuit works together to reduce output ripple, and the main power path can suppress flicker without large-capacity electrolytic capacitors, improving conversion efficiency. The auxiliary power supply circuit 7 extracts a stable low-voltage power supply from the high-voltage side of the boost circuit 2 to provide isolated power supply for the control module, avoiding signal path interference from the main power. Through the coordinated work of the boost circuit and the flyback buck circuit, the output rectifier circuit only needs small-capacity electrolytic capacitors for filtering, which can effectively improve conversion efficiency and reduce losses. Compared with the traditional single-stage flyback flicker-reducing IC circuit solution, the two-stage solution is more cost-effective, more efficient, and smaller in size.Furthermore, the thyristor detection circuit 4 accurately extracts the conduction angle signal through a voltage reference chip and a transistor-MOSFET cascade structure, and combines optocoupler isolation to achieve high anti-interference square wave signal conversion, which can effectively eliminate signal distortion caused by dimmer impedance differences; the analog dimming to PWM dimming circuit 6 directly achieves linear conversion of analog signal to PWM signal through a dimming conversion chip, and uses isolated power supply and internal chip algorithm to eliminate signal distortion, ensuring high precision and anti-interference of dimming control; the thyristor dimming to analog dimming circuit 5 filters out signal noise and stabilizes output through a filter rectifier network and transistor buffer structure, and uses discrete components to achieve high precision conversion of square wave to analog voltage; the flyback buck circuit 3 achieves precise regulation of LED current through the coordinated control of dimming control chip and PWM signal, and combines the high-efficiency energy conversion structure of transformer and MOSFET, which can simplify the driving logic while reducing output ripple, suppress flicker and improve the overall conversion efficiency without large-capacity filter components; the flyback buck circuit 3 achieves self-powered operation through auxiliary winding and transistor voltage regulation structure, and uses diode and reference voltage to stabilize control. The chip power supply simplifies the power supply circuit while improving system reliability and preventing chip damage caused by high voltage fluctuations. Voltage and current detection circuits perform voltage division sampling and a filtering network to accurately feedback the output status. Combined with dual-loop closed-loop control, the PWM duty cycle is dynamically adjusted to improve LED current control accuracy. The output rectifier circuit adopts a dual-diode full-wave rectification and inductor filtering design. The primary and secondary dual-filter structure effectively suppresses high-frequency ripple, achieving small-capacity filtering while reducing component count, thus reducing power supply ripple and circuit size. Boost circuit 2 uses an APFC control chip to drive an inductor-MOSFET topology for high-efficiency power factor correction. Combined with diode and capacitor synergy, it stably outputs high-voltage DC over a wide voltage input range, improving overall energy efficiency while reducing grid harmonic interference. It is highly compatible and compact. Power module 1 uses an active damping circuit to suppress thyristor conduction surge current and utilizes MOSFETs and diodes to protect the rectifier bridge from voltage spikes. Combined with a two-stage EMI filtering design, it effectively suppresses noise and provides system safety protection, reducing component costs and improving reliability.

[0065] In summary, this invention solves the technical problems of poor compatibility between thyristor dimming and PWM dimming, as well as the large circuit size and low efficiency in the prior art.

[0066] The above description is only a preferred embodiment of the present utility model and does not limit the patent scope of the present utility model. All equivalent structural transformations made under the inventive concept of the present utility model using the contents of the present utility model specification and drawings, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present utility model.

Claims

1. A thyristor-to-PWM LED dimming circuit, characterized in that, include: The power module (1) has an input terminal connected to a thyristor dimmer, which is used to convert phase-cut AC power into primary DC voltage; The boost circuit (2) has its input terminal connected to the output terminal of the power module (1) and is used to boost the primary DC voltage to high voltage DC voltage. The flyback buck circuit (3) has its input terminal connected to the output terminal of the boost circuit (2) and is used to convert the high voltage DC power into a first DC power to power the LED load. The thyristor detection circuit (4) has its input terminal connected to the AC side of the power supply module (1) and is used to extract the thyristor conduction angle signal and generate a square wave signal. The thyristor dimming to analog dimming circuit (5) has its input terminal connected to the output terminal of the thyristor detection circuit (4) and is used to convert the square wave signal into an analog voltage signal. The analog dimming to PWM dimming circuit (6) has its input end connected to the output end of the thyristor dimming to analog dimming circuit (5) and its output end connected to the PWM control end of the flyback buck circuit (3), which is used to convert the analog voltage signal into a PWM control signal. The auxiliary power supply circuit (7) has its input end connected to the output end of the boost circuit (2) and is used to convert the high voltage DC power into a second DC power to power the control module in the circuit.

2. The thyristor-to-PWM LED dimming circuit as described in claim 1, characterized in that, The thyristor detection circuit (4) includes a voltage reference chip, a first transistor, a first MOS transistor, and an optocoupler; the reference terminal of the voltage reference chip is connected to the AC input terminal of the power supply module (1) to detect the thyristor conduction angle signal and generate a square wave signal at the output terminal; the emitter of the first transistor is connected to the output terminal of the auxiliary power supply circuit (7), and the base is connected to the output terminal of the voltage reference chip to amplify the square wave signal; the gate of the first MOS transistor is connected to the collector of the first transistor, the drain is connected to the output terminal of the auxiliary power supply circuit (7) and the first input terminal of the optocoupler, and the source and the second input terminal of the optocoupler are grounded; the output terminal of the optocoupler generates an isolated square wave signal.

3. The thyristor-to-PWM LED dimming circuit as described in claim 2, characterized in that, The analog dimming to PWM dimming circuit (6) includes a dimming conversion chip; the first input terminal of the dimming conversion chip is connected to the output terminal of the auxiliary power supply circuit (7), and the second input terminal is connected to the output terminal of the thyristor dimming to analog dimming circuit (5); the first output terminal of the dimming conversion chip is connected to the PWM control terminal of the flyback buck circuit (3), which is used to convert the analog voltage signal into a PWM control signal and adjust the LED load current.

4. The thyristor-to-PWM LED dimming circuit as described in claim 3, characterized in that, The thyristor-controlled dimming to analog dimming circuit (5) includes a second transistor, a first resistor, and a filter and rectifier circuit; the first output terminal of the optocoupler is connected to the second output terminal of the dimming conversion chip through the first resistor; the second output terminal of the optocoupler is grounded, and the first output terminal is connected to the base of the second transistor through the filter and rectifier circuit; the collector of the second transistor is connected to the second output terminal of the dimming conversion chip, and the emitter is connected to the second input terminal of the dimming conversion chip.

5. The thyristor-to-PWM LED dimming circuit as described in claim 1, characterized in that, The flyback buck circuit (3) includes a dimming control chip, a first transformer, and a second MOS transistor. The first input terminal of the dimming control chip is connected to the output terminal of the boost circuit (2), the second input terminal is connected to the output terminal of the analog dimming to PWM dimming circuit (6), and the driving terminal is connected to the gate of the second MOS transistor. The first end of the primary winding of the first transformer is connected to the output terminal of the boost circuit (2), and the second end is connected to the drain of the second MOS transistor. The source of the second MOS transistor is grounded.

6. The thyristor-to-PWM LED dimming circuit as described in claim 5, characterized in that, The flyback buck circuit (3) further includes a third transistor, a first diode, and a second diode; the anode of the first diode is connected to the first end of the auxiliary winding of the first transformer, and the second end of the auxiliary winding of the first transformer is grounded; the collector of the third transistor is connected to the cathode of the first diode, the emitter is connected to the first input terminal of the dimming control chip, and the base is connected to the anode of the second diode; the cathode of the second diode is grounded.

7. The thyristor-to-PWM LED dimming circuit as described in claim 6, characterized in that, The flyback buck circuit (3) further includes a voltage detection circuit and a current detection circuit; the voltage detection circuit includes a second resistor, a third resistor and a first capacitor, the first end of the second resistor is connected to the first end of the auxiliary winding of the first transformer, the second end of the second resistor, the first end of the third resistor and the first end of the capacitor are connected to the third input terminal of the dimming control chip, and the second end of the third resistor and the second end of the first capacitor are grounded; the current detection circuit includes a fourth resistor, a fifth resistor and a second capacitor, the first end of the fourth resistor and the first end of the second capacitor are connected to the fourth input terminal of the dimming control chip, the second end of the fourth resistor and the first end of the fifth resistor are connected to the source of the second MOS transistor, and the second end of the fifth resistor and the second end of the second capacitor are grounded.

8. The thyristor-to-PWM LED dimming circuit as described in claim 1, characterized in that, It also includes an output rectifier circuit (8), which includes two diodes, a first inductor, a primary filter circuit, and a secondary filter circuit. The first end of the two diodes is connected to the output end of the flyback buck circuit (3), and the second end of the two diodes is connected to the first input end of the first inductor. The second input end of the first inductor is grounded, and the output end is used to power the LED load. The primary filter circuit is connected between the first and second ends of the two diodes, and the secondary filter circuit is connected between the second end of the two diodes and ground.

9. The thyristor-to-PWM LED dimming circuit as described in claim 1, characterized in that, The boost circuit (2) includes an APFC control chip, a second inductor, a third MOSFET, a fourth capacitor, and a third diode; the first end of the second inductor, the anode of the third diode, and the drain of the third MOSFET are all connected to the output terminal of the power module (1); the second end of the second inductor and the cathode of the third diode are all connected to the first end of the fourth capacitor; the first input terminal of the APFC control chip is connected to the output terminal of the auxiliary power supply circuit (7), and the driving terminal is connected to the gate of the third MOSFET; the source of the third MOSFET is grounded.

10. The thyristor-to-PWM LED dimming circuit as described in claim 1, characterized in that, The power module (1) includes a rectifier bridge, a fourth diode, a sixth resistor, and a fourth MOS transistor; the first DC output terminal of the rectifier bridge is connected to the gate of the fourth MOS transistor and the cathode of the fourth diode, the second DC output terminal of the rectifier bridge is connected to the anode of the fourth diode, the first terminal of the sixth resistor, and the source of the fourth MOS transistor, and the drain of the fourth MOS transistor and the second terminal of the sixth resistor are grounded.

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