Dimming power supply, quick turn-off circuit and method and lighting system

Abstract

The invention relates to the technical field of power supply illumination, in particular to a dimming power supply, a quick turn-off circuit, a quick turn-off method and an illumination system. The dimming power supply is provided with a quick turn-off circuit. And the quick turn-off circuit uses two diodes to form an external power detection unit for detecting the on-off state of an external power supply, and uses two triodes to form a judgment output unit, so that the power supply of the step-down chip can be cut off under the condition that the external power supply is detected to be cut off. According to the dimming power supply provided by the invention, the on-off state of the external power supply is detected through the quick turn-off circuit, and the power supply of the step-down chip is cut off under the condition that the external power supply is cut off, so that the quick turn-off of the output of the dimming power supply is realized. Under the scene of the tube spotlight and the LED lamp strip, the dimming power supply provided by the invention is used for supplying power to the LED lamp strip, when the tube spotlight is turned off, the LED lamp strip and the tube spotlight can be synchronously and instantly turned off, residual light is not left, brightness decay is not generated, turning-off trailing is not generated, and turning-off delay of the LED lamp strip and the tube spotlight cannot be sensed by naked eyes completely.

Description

Technical Field

[0001] This invention relates to the field of power supply and lighting technology, and in particular to a dimming power supply, a fast shutdown circuit, a method, and a lighting system. Background Technology

[0002] In existing lighting systems, especially in indoor scenarios where downlights and LED strips are used in combination, deep dimming and synchronized start / stop have become core requirements for dimming performance. However, current dimming power supply solutions on the market still have significant technical deficiencies when dealing with this type of composite lighting structure. Specifically, downlights typically use low-power constant current drivers with small energy storage capacity and short discharge paths, allowing them to quickly shut off after power failure in low-brightness conditions. In contrast, LED strips generally use high-power constant voltage drivers, whose output terminals are usually equipped with large-capacity filter capacitors to maintain voltage stability. This results in the LED strip remaining lit even after the control signal has been cut off in low-brightness dimming conditions due to the slow discharge of residual charge, causing a significant shutdown delay.

[0003] The inherent differences between the two types of power supplies in terms of energy storage structure, discharge capacity, and dimming topology design are significantly amplified during deep dimming (especially near the off state). This results in a noticeable time difference between downlights and LED strips during synchronous shutdown, severely impacting visual consistency and the quality of the dimming finish. Existing technologies commonly employ ordinary shutdown mechanisms, which are only suitable for single LED strips or simple lighting scenarios without synchronization requirements. They cannot meet the stringent experience demands of high-end residential and commercial spaces for "deep dimming + synchronous start-stop." Therefore, effectively improving the shutdown speed of LED strips to achieve synchronous shutdown with constant current loads such as downlights has become a critical technical problem urgently needing to be solved in the field of dimming power supplies. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing dimming power supplies in that the turn-off speed of LED light strips is relatively slow, and to provide a dimming power supply, a fast turn-off circuit, a method, and a lighting system.

[0005] In a first aspect, the present invention provides a dimming power supply. The dimming power supply includes: a fast shutdown circuit for detecting the on / off state of an external power supply and disconnecting the power supply to a step-down chip when the external power supply is disconnected. The fast shutdown circuit includes an external power detection unit and a judgment output unit. The external power detection unit includes diodes D15 and D16. The anodes of diodes D15 and D16 are respectively connected to the live wire and neutral wire of the external power supply. The cathodes of diodes D15 and D16 are connected to... The judgment output unit includes transistors Q5 and Q6. The collector of transistor Q5 is connected to the power supply terminal VCC, the emitter of transistor Q5 is connected to the power supply terminal VCC1 of the step-down chip, and the base of transistor Q5 is connected to the emitter of transistor Q6. The collector of transistor Q6 is grounded, and the base of transistor Q6 is connected to the cathodes of diodes D15 and D16 through at least one resistor. The base of transistor Q6 is also grounded through resistor R52.

[0006] According to a preferred embodiment, the dimming power supply further includes a filtering, rectification, and surge protection circuit. The filtering, rectification, and surge protection circuit includes: two power input terminals for connecting the live wire and neutral wire of an external power supply, respectively; a first filtering unit, which uses common-mode inductors LF2 and LF3 to form a composite electromagnetic interference filtering circuit for filtering noise signals; and a rectification unit, which uses diodes D10, D11, D12, and D13 to form a full-wave rectifier bridge for rectifying AC signals into DC signals.

[0007] According to a preferred embodiment, the dimming power supply further includes an active power factor correction boost circuit. The active power factor correction boost circuit is built based on a constant voltage control chip and is used to make the input current waveform follow the input voltage waveform and to boost the voltage. The active power factor correction boost circuit includes: a second filtering unit, which uses a differential-mode inductor L1, resistor R3, and capacitor CX1 to form a differential-mode filter circuit, used to obtain the output of the filtering, rectification, and surge protection circuit and suppress electromagnetic interference on the power line; a boost unit, which uses a transformer T1, power MOSFET Q1, diode D1, diode D2, and capacitor C1 to form a first power conversion circuit, used to boost the output of the filtering unit; and a boost control unit, built using a constant voltage control chip U3, which controls the switching frequency and duty cycle of the power MOSFET Q1 by detecting the output feedback of the boost unit and current sampling.

[0008] According to a preferred embodiment, the dimming power supply further includes a flyback buck circuit. The flyback buck circuit includes: a buck unit, comprising a transformer T2A, a power MOSFET Q4, and a diode D9 forming a second power conversion circuit for bucking the output of the active power factor correction boost circuit; a buck control unit, constructed using a buck chip U6, for controlling the switching frequency and duty cycle of the power MOSFET Q4; and a first auxiliary power supply unit, comprising a transformer T2B, diodes D19, D20, D21, and a transistor Q9, for supplying power to the buck control unit; the output VCC of the first auxiliary power supply unit is connected to the fast shutdown circuit.

[0009] According to a preferred embodiment, the dimming power supply further includes an output rectifier circuit for rectifying and filtering the output of the flyback buck circuit.

[0010] According to a preferred embodiment, the dimming power supply further includes a dimming and color-tuning circuit, which uses a power switch controller to control the duty cycle of two PWM signals.

[0011] According to a preferred embodiment, the dimming power supply further includes an auxiliary power supply circuit, which processes the output of the output rectifier circuit to supply power to the power switch controller of the dimming and color-tuning circuit.

[0012] In a second aspect, the present invention also provides a fast shutdown circuit for a dimming power supply, comprising: an external power detection unit and a judgment output unit. The external power detection unit is used to detect the on / off state of the external power supply. The judgment output unit is used to disconnect the power supply to the step-down chip when the external power supply is disconnected. The external power detection unit includes diodes D15 and D16. The anodes of diodes D15 and D16 are respectively connected to the live wire and neutral wire of the external power supply, and the cathodes of diodes D15 and D16 are connected to... The judgment output unit includes transistors Q5 and Q6. The collector of transistor Q5 is connected to the power supply terminal VCC, the emitter of transistor Q5 is connected to the power supply terminal VCC1 of the step-down chip, and the base of transistor Q5 is connected to the emitter of transistor Q6. The collector of transistor Q6 is grounded, and the base of transistor Q6 is connected to the cathodes of diodes D15 and D16 through at least one resistor. The base of transistor Q6 is also grounded through resistor R52.

[0013] In a third aspect, the present invention also provides a dimming method, which uses a dimming power supply provided by the present invention for dimming.

[0014] In a fourth aspect, the present invention also provides a lighting system, the light source including an LED light strip and downlights. The LED light strip is dimmed using a dimming power supply provided by the present invention.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0016] This invention provides a dimming power supply that detects the on / off state of an external power supply through a rapid shutdown circuit. When the external power supply is disconnected, the power supply to the step-down chip is cut off, thereby achieving rapid shutdown of the dimming power supply output. The LED light strip and the downlight will turn off instantly and synchronously, with no residual light, no brightness decay, and no trailing afterglow. The entire shutdown process takes a short time, and the shutdown delay of the LED light strip and the downlight is completely imperceptible to the naked eye, thus achieving a synchronous shutdown effect. Moreover, the low-brightness shutdown effect is basically the same as the high-brightness shutdown effect, and the dimming end is clean and neat, which better meets the customer's demanding requirements for deep dimming. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of a dimming power supply circuit according to a preferred embodiment of the present invention.

[0018] Figure 2 This is a schematic diagram of a fast shutdown circuit according to a preferred embodiment of the present invention.

[0019] Figure 3 This is a schematic diagram of a preferred embodiment of the filtering and rectification surge protection circuit of the present invention.

[0020] Figure 4 This is a schematic diagram of an active power factor correction boost circuit according to a preferred embodiment of the present invention.

[0021] Figure 5 This is a schematic diagram of a flyback buck circuit according to a preferred embodiment of the present invention.

[0022] Figure 6 This is a schematic diagram of the output rectifier circuit according to a preferred embodiment of the present invention.

[0023] Figure 7 This is a schematic diagram of a dimming and color-tuning circuit according to a preferred embodiment of the present invention.

[0024] Figure 8 This is a schematic diagram of an auxiliary power supply circuit according to a preferred embodiment of the present invention. Detailed Implementation

[0025] The present invention will now be described in further detail with reference to specific embodiments. However, this should not be construed as limiting the scope of the present invention to the following embodiments; all technologies implemented based on the content of the present invention fall within the scope of the present invention.

[0026] Unless otherwise specified, the terms "upper," "lower," "left," "right," "center," "inner," and "outer," etc., used in the description of specific embodiments of the present invention to indicate orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings, or the orientation or positional relationship in which the product / equipment / device is usually placed during use. These terms are merely for the purpose of facilitating the description of the present invention or simplifying the description in specific embodiments, and for enabling those skilled in the art to quickly understand the solution, and do not indicate or imply that a particular device / component / element must have a specific orientation, or be constructed and operated in a specific positional relationship. Therefore, they should not be construed as limitations on the present invention.

[0027] Furthermore, the use of terms such as "horizontal," "vertical," "suspended," "parallel," and "coaxial" does not imply that the corresponding device / component / element must be absolutely horizontal, vertical, suspended, parallel, or coaxial. Slight tilt or deviation is permissible, as long as it does not affect the normal function of the relevant component. For example, "horizontal" simply means that its direction is more horizontal relative to "vertical," not that the structure must be perfectly horizontal; a slight tilt is acceptable. "Coaxial" means that two components are arranged as coaxially as possible, allowing them to move coaxially or approximately coaxially when their relative positions change. Alternatively, it can be simplified to mean that the corresponding device / component / element, when arranged in "horizontal," "vertical," "suspended," "parallel," or "coaxial" directions, can have an error / deviation of ±10% relative to the corresponding direction, more preferably within ±8%, more preferably within ±6%, more preferably within ±5%, and more preferably within ±4%. For example, the deviation in the "coaxial" direction is controlled within 0.2-1mm, preferably within 0.2-0.5mm. As long as the corresponding device / component / element is within the error / deviation range, it can still achieve its function in the solution of the present invention.

[0028] Furthermore, the use of terms such as "first," "second," and "third" in terminology is merely for distinguishing descriptions of identical or similar components and should not be interpreted as emphasizing or implying the relative importance of a particular component.

[0029] Furthermore, in the description of the embodiments of the present invention, "several", "more than", and "a number of" represent at least two. The number can be any number, such as two, three, four, five, six, seven, eight, or nine, and can even exceed nine.

[0030] Furthermore, in the description of the technical solution of this invention, unless otherwise explicitly specified / limited / restricted, the terms "set up," "install," "connect," "link," "provided with," "laid out," and "arranged" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to connection methods commonly used in the art, such as welding, riveting, bolting, and threaded connections. Such connections can be mechanical, electrical, or communication connections; they can be direct connections or indirect connections through an intermediate medium; and they can refer to the internal communication between two components.

[0031] Example 1 This embodiment provides a dimming power supply. See also... Figure 1 and Figure 2 The dimming power supply is equipped with a fast shutdown circuit, which detects the on / off status of the external power supply and disconnects the power supply to the buck chip when the external power supply is disconnected.

[0032] See Figure 1 The fast shutdown circuit includes an external power detection unit and a judgment output unit. The external power detection unit includes diodes D15 and D16. The anodes of diodes D15 and D16 are connected to the live wire and neutral wire of the external power supply, respectively, and the cathodes of diodes D15 and D16 are connected to...

[0033] The output unit is determined by transistors Q5 and Q6.

[0034] The collector of transistor Q5 is connected to the power supply terminal VCC, the emitter of transistor Q5 is connected to the power supply terminal VCC1 of the step-down chip, and the base of transistor Q5 is connected to the emitter of transistor Q6.

[0035] The collector of transistor Q6 is grounded, and the base of transistor Q6 is connected to the cathode of diodes D15 and D16 through at least one resistor. The base of transistor Q6 is also grounded through resistor R52.

[0036] The dimming power supply provided in this embodiment detects the on / off status of the external power supply through a fast shutdown circuit. When the external power supply is disconnected, the power supply to the step-down chip is cut off, thereby achieving rapid shutdown of the dimming power supply output. Especially in scenarios involving downlights and LED strips, using the dimming power supply provided in this embodiment to power the LED strip results in the LED strip turning off synchronously and instantly with the downlight when the lights are turned off. There is no residual light, no brightness decay, and no trailing afterglow. The entire shutdown process is short, and the turning-off delay between the LED strip and the downlight is completely imperceptible to the naked eye, thus achieving a synchronous shutdown effect. Furthermore, the low-brightness shutdown effect is essentially the same as the high-brightness shutdown effect, resulting in a clean and crisp dimming finish that better meets customers' stringent requirements for deep dimming.

[0037] Example 2 This embodiment is a further improvement on embodiment 1, and the repeated content will not be described again.

[0038] See Figure 1 The dimming power supply also includes: a filtering and rectification circuit for lightning and surge protection, an active power factor correction boost circuit, a flyback buck circuit, an output rectifier circuit, a dimming and color-adjusting circuit, and an auxiliary power supply circuit.

[0039] The external power supply is connected to the input terminal of the filter, rectifier, and surge protection circuit. This circuit has two output terminals: the first output terminal is connected to the input terminal of the fast shutdown circuit, and the second output terminal is connected to the input terminal of the active power factor correction boost circuit. The output terminal of the active power factor correction boost circuit is connected to the input terminal of the flyback buck circuit. The output terminal of the flyback buck circuit is connected to the input terminal of the output rectifier circuit. The output rectifier circuit has three output terminals: the first output terminal is connected to the power supply terminal of the LED strip; the second output terminal is connected to the input terminal of the dimming and color-tuning circuit; and the third output terminal is connected to the input terminal of the auxiliary power supply circuit.

[0040] See Figure 1 and Figure 3 The filtering and rectifying surge protection circuit includes two power input terminals, a first filtering unit, and a rectifier unit.

[0041] Two power input terminals are used to connect to the live and neutral wires of an external power supply, respectively. The first filtering unit uses common-mode inductors LF2 and LF3 to form a composite electromagnetic interference filter circuit to filter out noise signals. The rectifier unit uses diodes D10, D11, D12, and D13 to form a full-wave rectifier bridge to rectify AC signals into DC signals.

[0042] Specifically, the two power input terminals include input terminal L3 and input terminal N1. Input terminal L3 is connected to one input terminal of common-mode inductor LF3 via F1, and input terminal N1 is connected to the other input terminal of common-mode inductor LF3 via variable resistor RT1. RT1 is an NTC thermistor (negative temperature coefficient thermistor), a component whose resistance decreases as temperature increases. The two input terminals of common-mode inductor LF3 are connected to the two ends of variable resistor RV2. The two output terminals of common-mode inductor LF3 are connected to the two input terminals of common-mode inductor LF2. Resistors R44 and R55 are connected in series to the two output terminals of common-mode inductor LF3. Capacitor CX2 is connected to the two input terminals of common-mode inductor LF2. The two output terminals of common-mode inductor LF2 are respectively led out to the live wire detection port L and the neutral wire detection port N. The live wire detection port L and the neutral wire detection port N form the first output terminal of the filter rectification surge protection circuit, which is used to connect to the input terminal of the fast shutdown circuit.

[0043] The two output terminals of common-mode inductor LF2 are connected to the two ends of variable resistor RV1. Diodes D10, D11, D12, and D13 form a full-wave rectifier bridge. The cathode of D10 is connected to the cathode of D12, the anode of D12 is connected to the cathode of D13, the anode of D13 is connected to the anode of D11, and the cathode of D11 is connected to the anode of D10. The output terminal of the common-mode inductor LF2 from the live wire detection port L is connected between diodes D10 and D11, and the output terminal of the common-mode inductor LF2 from the neutral wire detection port N is connected between diodes D12 and D13. The anodes of diodes D11 and D13 are used as one output terminal of the filtering, rectification, and surge protection circuit; the cathodes of diodes D10 and D12 are used as the other output terminal of the filtering, rectification, and surge protection circuit.

[0044] Input terminals L3 and N1 are also connected to COM3, which is a terminal block for connecting to an external power supply. Pins 1 and 2 of COM3 are connected to input terminal L3, pins 5 and 6 of COM3 are connected to input terminal N1, and pins 3 and 4 of COM3 are connected to each other and left floating.

[0045] See Figure 1 and Figure 4 The active power factor correction boost circuit includes: a second filter unit, a boost unit, and a boost control unit.

[0046] The second filtering unit uses a differential-mode filter circuit composed of differential-mode inductor L1, resistor R3 and capacitor CX1 to obtain the output of the filtering, rectification and surge protection circuit and suppress electromagnetic interference on the power line.

[0047] The boost unit uses transformer T1, power MOSFET Q1, diode D1, diode D2 and capacitor C1 to form the first power conversion circuit, which is used to boost the output of the filter unit.

[0048] The boost control unit is built using the constant voltage control chip U3. By detecting the output feedback of the boost unit and sampling the current, it controls the switching frequency and duty cycle of the power MOSFET Q1.

[0049] Active power factor correction (APCC) boost circuits control switching components to make the input current waveform follow the input voltage waveform, thereby suppressing harmonics and improving the power factor. Improving the power factor not only suppresses grid harmonics but also reduces input current and power consumption. APC boost circuits can improve grid efficiency and electromagnetic compatibility (EMC).

[0050] Specifically, the cathodes of diodes D10 and D12 are connected to one end of the differential-mode inductor L1, and the anodes and cathodes of diodes D11 and D13 are connected to one end of the differential-mode inductor L1 through capacitor CB1. One end of capacitor CX1 is connected to the cathode of diode D10, and the other end is connected to the anode of diode D11. The end of capacitor CX1 connected to the anode of diode D11 is also connected to ground IC-GND. The differential-mode inductor L1 is connected in parallel with resistor R3. The differential-mode inductor L1 is connected to one end of capacitor CB1. The current after passing through the differential-mode inductor L1 is VBUS. VBUS represents the voltage after rectification and filtering, and in this embodiment, it can represent the potential symbol of the 310V DC formed after the 220V AC external power supply is rectified and filtered by a full-bridge rectifier.

[0051] One end of the differential-mode inductor L1 and capacitor CB1 is connected to the positive primary winding of transformer T1. The negative primary winding of transformer T1 is connected to the anode of diode D2. The anode of diode D1 is connected to the positive primary winding of transformer T1, and the cathode of diode D1 is connected to the cathode of diode D2. Capacitor C1 is connected in parallel with diode D1. The cathode of diode D2 is connected to one end of resistor B1, and the other end of resistor B1 is connected to a flyback buck circuit.

[0052] The end of resistor B1 not connected to diode D2 is connected to one end of resistor R2. The other end of resistor R2 is connected to one end of resistor R8. The other end of resistor R8 is connected to one end of resistor R13. The other end of resistor R13 is grounded to IC-GND through capacitor C7. Resistor R19 is connected in parallel with capacitor C7. The end of resistor R13 connected to capacitor C7 is led out to port FB.

[0053] The constant voltage control chip U3 uses ICBP2628. Resistor R13 is connected to the FB port of the constant voltage control chip U3 to detect the voltage across the output electrolytic capacitor (capacitor EC1). This voltage is compared with the internal reference voltage of the constant voltage control chip U3, and after error amplification, the on-time of the MOSFET (power MOSFET Q1) is controlled to achieve constant voltage output.

[0054] The positive terminal of the secondary side of transformer T1 is connected to ground IC-GND. The negative terminal of the secondary side of transformer T1 is connected to the ZCD port of constant voltage control chip U3 through resistor R20. The anode of diode D2 is connected to the drain of MOSFET Q1. The drain of MOSFET Q1 is also connected to one end of resistor R11, and the other end of resistor R11 is connected to the source of MOSFET Q1 through capacitor C6. The source of MOSFET Q1 is connected to the CS port of constant voltage control chip U3 through resistor R21. Resistor R18 connects the source and gate of MOSFET Q1. The gate of MOSFET Q1 is connected to the anode of diode D6, and the cathode of diode D6 is connected to the GATE port of constant voltage control chip U3 through resistor R15. Resistor R12 is connected in parallel with diode D6. The VCC port of constant voltage control chip U3 is connected to the VPFC port. The VCC port of constant voltage control chip U3 is also connected to the anode of capacitor EC4, and the cathode of capacitor EC4 is connected to ground IC-GND. Capacitor C12 is connected in parallel with capacitor EC4. The COMP port of the constant voltage control chip U3 is grounded to IC-GND through capacitor C9. The COMP port of the constant voltage control chip U3 is also connected to one end of resistor R30, and the other end of resistor R30 is grounded to IC-GND through capacitor C11.

[0055] Preferably, the external power supply is 220V AC mains power, and the active power factor correction boost circuit boosts the voltage to 400V to supply the subsequent circuit.

[0056] See Figure 1 and Figure 2 The fast shutdown circuit includes an external power detection unit and a judgment output unit. The external power detection unit includes diodes D15 and D16. The judgment output unit includes transistors Q5 and Q6.

[0057] Specifically, the anode of diode D15 is connected to the live wire detection port L, and the anode of diode D16 is connected to the neutral wire detection port N. The cathodes of diodes D15 and D16 are connected together. Resistors R47, R48, and R49 are connected in series and then connected to the cathode of diode D15 and the base of transistor Q6.

[0058] The collector of transistor Q5 is connected to the power supply terminal VCC, the emitter of transistor Q5 is connected to the power supply terminal VCC1 of the step-down chip, and the base of transistor Q5 is connected to the emitter of transistor Q6. Resistor R43 connects the collector and base of transistor Q5.

[0059] The collector of transistor Q6 is grounded to IC-GND. The base of transistor Q6 is also grounded to IC-GND through resistor R52. Capacitor C20 is connected in parallel with resistor R52. The positive terminal of diode ZD1 is grounded to IC-GND, and the negative terminal is connected to the base of transistor Q6. Capacitor C19 is connected to the collector and emitter of transistor Q6.

[0060] See Figure 1 and Figure 5 The flyback buck circuit includes: a buck unit, a buck control unit, and a first auxiliary power supply unit.

[0061] The step-down unit, utilizing transformer T2A, power MOSFET Q4, and diode D9 to form a second power conversion circuit, is used to step down the output of the active power factor correction boost circuit. The step-down control unit, based on the step-down chip U6, is used to control the switching frequency and duty cycle of power MOSFET Q4.

[0062] The first auxiliary power supply unit, consisting of transformer T2B, diodes D19, D20, D21, and transistor Q9, is used to supply power to the step-down control unit. The output VCC of the first auxiliary power supply unit is connected to the fast shutdown circuit.

[0063] The input voltage of the flyback buck circuit (the voltage across capacitor EC1) is charged to the VDD pin of buck chip U6 through the start-up resistor (R10, R14, R22) and the transistor Q5 is saturated and turned on. When the VDD voltage reaches the start-up threshold, buck chip U6 is activated and the built-in soft start slowly increases the PWM duty cycle to avoid start-up shock and enter steady-state operation.

[0064] Then, steady-state energy transfer occurs. When the gate pin of the buck converter U6 outputs a high level, it drives the power MOSFET (power MOSFET Q4) to conduct, and the input voltage is applied to the primary winding of the transformer (T2). The inductor current rises linearly, and electrical energy is converted into magnetic energy and stored in the transformer core. At this time, the voltage of the secondary winding is reversed, the rectifier diode D5 is cut off, and there is no energy output from the secondary side of transformer T2. The load (LED light strip) is powered by the output capacitors (EC2, EC3).

[0065] When the SENS pin of the step-down chip U6 detects that the primary current of the transformer (T2) reaches the design threshold, the GATE pin outputs a low level, driving the power MOSFET (power MOSFET Q4) to turn off. The magnetic field of the transformer T2 core begins to decrease, the polarity of the secondary winding voltage reverses, the rectifier diode (D5) turns on, and the magnetic energy is converted into electrical energy, which is delivered to the load (LED light strip) and charges the output capacitors (EC2, EC3).

[0066] The U6 step-down chip repeats the above cycle using a fixed clock signal, while adjusting the peak current using the feedback signal from the PRT pin to achieve stable output voltage.

[0067] Specifically, the positive terminal of capacitor EC1 is connected to the output terminal of the active power factor correction boost circuit, i.e., resistor B1 is connected to one end of resistor R2. The negative terminal of capacitor EC1 is grounded to IC-GND. Capacitor C4 is connected in parallel with capacitor EC1. The positive terminal of capacitor EC1 is connected to one end of resistor R10, the other end of resistor R10 is connected to one end of resistor R14, the other end of resistor R14 is connected to resistor R22, and the other end of resistor R22 is connected to the VCC port. Resistors R5, R6, R7, and capacitor C3 are connected in parallel, with one end connected to the positive terminal of capacitor EC1 and the other end connected to the negative terminal of diode D9 through resistor R16. Resistor R17 is connected in parallel with resistor R16. The positive terminal of diode D9 is connected to the negative terminal of the primary winding of transformer T2A. One end of resistor R4 is connected to the positive terminal of the primary winding of transformer T2A, and the other end of resistor R4 is connected to the negative terminal of the primary winding of transformer T2A through capacitor C5. The positive terminal of the primary winding of transformer T2A is connected to the positive terminal of capacitor EC1.

[0068] The cathode of diode D9 is connected to the drain of power MOSFET Q4. The source of power MOSFET Q4 is grounded to IC-GND through resistor R50. The drain of power MOSFET Q4 is connected to one end of capacitor C14 through resistor R34, and the other end of capacitor C14 is connected to the source of power MOSFET Q4. The anode of diode D17 is connected to the source of power MOSFET Q4, and the cathode of diode D17 is connected to ground IC-GND. The gate of power MOSFET Q4 is connected to ground IC-GND through resistor R38.

[0069] The step-down chip U6 uses the OB2281.

[0070] The gate of power MOSFET Q4 is connected to the anode of diode D14. The cathode of diode D14 is connected to the GATE port of buck converter U6 via resistor R35. Resistor R36 is connected in parallel with diode D14. The GND port of buck converter U6 is connected to IC-GND. The VDD port of buck converter U6 is connected to the VCC1 port. The anode of capacitor EC5 is connected to the VDD port of buck converter U6, and the cathode is connected to ground IC-GND. Capacitor C15 is connected in parallel with capacitor EC5. The SENS port of buck converter U6 is grounded to IC-GND via capacitor C18. The SENS port of buck converter U6 is also connected to the anode of diode D17 via resistor R46. The FB port of buck converter U6 is connected to one end of resistor R39, and the other end of resistor R39 is grounded to IC-GND via capacitor C17. Optocoupler U7B is connected in parallel with capacitor C17.

[0071] The negative terminal of the secondary side of transformer T2B is grounded to IC-GND. Resistors R59 and R60 each have one end connected to the positive terminal of the secondary side of transformer T2B. The other end of resistor R59 is connected to the anode of diode D19, and the other end of resistor R60 is grounded to IC-GND through resistor R62. Capacitor C23 is connected in parallel with resistor R62. Capacitor C23 is connected to one end of resistor R60 and also to the PRT port of the step-down chip U6. The anode of capacitor EC8 is connected to the cathode of diode D19, and the cathode is connected to ground IC-GND. The anode of diode ZD2 is connected to ground IC-GND, and the cathode is connected to the collector of transistor Q9 through resistor R61. The base of transistor Q9 is connected to the cathode of diode ZD2. The emitter of transistor Q9 is connected to the anode of diode D20. The emitter of transistor Q9 is also connected to the anode of diode D21. The cathode of diode D20 is connected to the VCC port. The cathode of diode D21 is connected to the VPFC port. The VCC port is connected to a fast shutdown circuit, that is, the negative terminal of diode D20 is connected to the collector of transistor Q5.

[0072] T2A and T2B are the same isolation transformer T2, sharing the same primary side. T2A and T2B are used to distinguish the different output secondary sides of transformer T2.

[0073] The fast shutdown circuit detects the switch of AC power in the power grid. When the power is turned off, transistor Q6 turns on and transistor Q5 turns off, disconnecting the step-down chip U6, thereby achieving fast shutdown.

[0074] The flyback buck circuit reduces the 400V voltage to the designed output voltage through an isolation transformer via the flyback topology. The output voltage value can be determined based on the parameters of the isolation transformer T2 (T2A, T2B), buck converter U6, and U5, and is the rectified output voltage obtained through the step-down process.

[0075] See Figure 1 and Figure 6 The output rectifier circuit is used to rectify and filter the output of the flyback buck circuit, that is, to rectify and filter the secondary output of transformer T2A.

[0076] The flyback buck circuit still outputs a pulsating waveform, which cannot be directly used for LED chip loads and requires rectification and filtering. The output rectifier circuit, through diode rectification and electrolytic capacitor energy storage and filtering, can supply power to the load after it is connected, while also filtering out noise signals in the current.

[0077] Specifically, the positive terminal of the secondary side of transformer T2A is connected to ground SGND1. The negative terminal of the secondary side of transformer T2A is connected to the positive terminal of diode D5, and the negative terminal of diode D5 is grounded to SGND1 through resistor R9. Capacitors EC2 and EC3 are connected in parallel, and the positive terminal of the parallel connection is connected to the negative terminal of diode D5, and the negative terminal of the parallel connection is grounded to SGND1. The positive terminal of diode D5 is connected to one end of resistor R1, the other end of resistor R1 is connected to capacitor C2, and the other end of capacitor C2 is connected to the negative terminal of diode D5. The negative terminal of diode D5 is led out to the VOUT port.

[0078] The VOUT port is connected to one end of resistor R24, and the other end of resistor R24 ​​is connected to the cathode of the adjustable shunt voltage reference chip U5 via optocoupler U7A. The adjustable shunt voltage reference chip U5 is a TL431. The anode of the adjustable shunt voltage reference chip U5 is grounded to SGND1. Resistor R29 is connected in parallel with U7A. Resistors R41 and R42 are connected in parallel, with one end grounded to SGND1 and the other end connected to the reference terminal of the adjustable shunt voltage reference chip U5. The reference terminal of the adjustable shunt voltage reference chip U5 is also connected to one end of resistor R25, and the other end of resistor R25 is connected to the VOUT port. One end of capacitor C13 is connected to the cathode of diode U5, and the other end is grounded to SGND1 via resistor R42. One end of resistor R33 is connected to the cathode of diode U5, and the other end is connected to the node between resistors R42 and R25.

[0079] The VOUT port is connected to ground IC-GND through capacitor CY1. Ground IC-GND is connected to ground SGND1 through capacitor CY2. VOUT is the output voltage, IC-GND is the primary reference ground, and SGND1 is the secondary reference ground.

[0080] The VOUT port is connected to the first input port of inductor LF1, and the first output port of inductor LF1 is connected to pins 1 and 2 of COM1, forming LED+1. LED+1 is used to connect to the positive terminal of the LED strip.

[0081] The negative terminal of diode D3 is connected to the VOUT port, and the positive terminal is connected to the second input port of inductor LF1; the second output port of inductor LF1 is connected to pins 3 and 4 of COM1, forming LEDC-1. LEDC-1 is used to connect to the cold light negative terminal of the LED strip.

[0082] The negative terminal of diode D4 is connected to the VOUT port, and the positive terminal is connected to the third input port of inductor LF1; the third output port of inductor LF1 is connected to pins 5 and 6 of COM1, forming LEDW-1. LEDW-1 is used to connect to the warm light negative terminal of the LED strip.

[0083] Inductor LF1 is a filter inductor used to suppress load interference. COM1 is an output terminal used to connect LED strip lights.

[0084] See Figure 1 and Figure 7 The dimming and color-adjusting circuit is composed of a power switch controller and COM2, which outputs two PWM signals to achieve dimming and color adjustment.

[0085] Specifically, the dimming and color-tuning circuit uses two power switch controllers, U2 and U4. The power switch controllers are N531. The anode of diode D3 is connected to the drain of power MOSFET Q3. The source of power MOSFET Q3 is connected to ground SGND1 through resistor R31. The gate of power MOSFET Q3 is connected to the anode of diode D7. The cathode of diode D7 is connected to the Vout port of power switch controller U4. Resistor R23 is connected in parallel with diode D7. Resistor R27 connects the gate and source of power MOSFET Q3. The VCC port of power switch controller U4 is connected to the 5V port. The GND port and VIN port of power switch controller U4 are connected through resistor R40. The GND port of power switch controller U4 is connected to ground SGND1. The VIN port of power switch controller U4 is connected to the PWM-C port. Power switch controller U2 is used to control warm light, and power switch controller U4 is used to control cool light.

[0086] The anode of diode D4 is connected to the drain of power MOSFET Q2. The source of power MOSFET Q2 is connected to the Io port via resistor R32. The gate of power MOSFET Q3 is connected to the anode of diode D8. The cathode of diode D8 is connected to the Vout port of power switch controller U2. Resistor R26 is connected in parallel with diode D8. Resistor R28 is connected to the gate and source of power MOSFET Q4. The VCC port of power switch controller U2 is connected to the 5V port. The VCC port of power switch controller U2 is also grounded to SGND1 via capacitor C8. The GND port and VIN port of power switch controller U2 are connected via resistor R37. The GND port of power switch controller U2 is connected to ground SGND1. The VIN port of power switch controller U2 is connected to the PWM-M port.

[0087] Pins 1 to 5 of COM2 are connected sequentially to the PWM-C port, PWM-M port, Io port, 5V port, and ground SGND1.

[0088] COM2 can be a control module used to control the color and brightness of the LED strip. The IO port is for output short-circuit protection. In the event of a short circuit in the LED strip, the control module controls the PWM-C port and the PWM-M port to output a low level based on the short-circuit signal transmitted by the IO port. That is, when a short circuit is detected in the LED strip, the LED strip will not light up, thus preventing power from being supplied to the short-circuited LED strip.

[0089] See Figure 1 and Figure 8 The auxiliary power supply circuit processes the output of the output rectifier circuit to power the power switch controllers U2 and U4 of the dimming and color tuning circuit. The auxiliary power supply circuit is based on optocoupler U8 and transistors Q7 and Q8. Optocoupler U8 is an OC5864.

[0090] Specifically, the VOUT port is connected to the base of transistor Q8 through resistor R53. The VOUT port is connected to the base of transistor Q7 through resistor R54. The base of transistor Q7 is connected to the collector of transistor Q8. The emitters of transistor Q7 and Q8 are grounded to SGND1. Resistor R57 connects the emitter and base of transistor Q8. The collector of transistor Q7 is connected to the EN port of optocoupler U8. The positive terminal of capacitor EC6 is connected to the VOUT port, and the negative terminal is connected to ground SGND1. The VOUT port is connected to the EN port of optocoupler U8 through resistor R51. The GND port of optocoupler U8 is connected to ground SGND1. The FB port of optocoupler U8 is connected to ground SGND1 through resistor R58. The FB port of optocoupler U8 is also connected to the 5V port through resistor R55. The IN port of optocoupler U8 is connected to the VOUT port. The IN port of optocoupler U8 is also connected to ground SGND1 through capacitor C21. Capacitor C16 connects to the VOUT port and the 5V port. The SW port of optocoupler U8 is connected to one end of inductor L2 via resistor B2, and the other end of inductor L2 is connected to the 5V port. The 5V port connected to inductor L2 is a reserved external port. One end of inductor L2 connected to resistor B2 is also connected to the cathode of diode D18, and the anode of diode D18 is connected to ground SGND1. Capacitor C22 is connected in parallel with diode D18. The anode of capacitor EC7 is connected to the 5V port, and the cathode is connected to ground SGND1. Resistor R56 is connected in parallel with capacitor EC7. The SGND port is connected to ground SGND1. SGND is a reserved external port.

[0091] The auxiliary power supply circuit processes the output of the output rectifier circuit and outputs a DC 5V to the COM2 module, and supplies power to the power switch controllers U2 and U4.

[0092] In this embodiment, AC power is first converted to DC power by a rectifier bridge, which is then fed to the front-end active power factor correction boost circuit for power factor correction, thereby improving the power factor and reducing grid losses. Then, by combining the front-end active power factor correction boost circuit with the rear-end flyback buck circuit, a wide voltage input is achieved and higher lightning surge capability is supported. At the same time, two PWM signals are added to the isolated output terminal to control the duty cycle of the MOSFET, adjust the average current of the LED strip, and achieve dimming and color adjustment effects.

[0093] Without a fast shutdown circuit (i.e., the negative terminal of diode D20 is directly connected to the VDD port of the step-down chip U6), when the external power supply is turned off, the LED strip turns off at its lowest brightness. However, because the electrolytic capacitor (capacitor EC1) still retains charge, the dimming power supply continues to operate, supplying power to the LED strip and preventing it from turning off immediately. This results in brightness decay and a trailing effect when the LED strip goes out, affecting the dimming effect. The off-time of the LED strip mainly depends on the capacitance of the electrolytic capacitor (capacitor EC1). The larger the capacitance of capacitor EC1, the longer the off-time of the LED strip.

[0094] After setting up the fast shutdown circuit, because the fast shutdown circuit captures the on / off status of the external power supply in real time, when the external power supply is on, the dimming power supply works normally; when the external power supply is off, the fast shutdown circuit cannot detect the external power supply, disconnects the power supply to the step-down chip U6, the step-down chip U6 stops working, the transformer T2 cannot perform energy conversion, and the stored electricity in the electrolytic capacitor (capacitor EC1) cannot be transferred to the LED light strip, thereby realizing the rapid shutdown of the output of the dimming power supply and realizing the immediate shutdown of the lights.

[0095] Example 3 This embodiment provides a fast shutdown circuit for a dimming power supply. The fast shutdown circuit includes: An external power detection unit is used to detect the on / off status of an external power supply. The external power detection unit includes diodes D15 and D16. The positive terminals of diodes D15 and D16 are connected to the live wire and neutral wire of the external power supply, respectively, and the negative terminals of diodes D15 and D16 are connected to... The output unit is used to disconnect the power supply to the step-down chip when the external power supply is disconnected. The output unit includes transistors Q5 and Q6. The collector of transistor Q5 is connected to the power supply terminal VCC, the emitter of transistor Q5 is connected to the power supply terminal VCC1 of the step-down chip, the base of transistor Q5 is connected to the emitter of transistor Q6, the collector of transistor Q6 is grounded, and the base of transistor Q6 is connected to the negative terminals of diodes D15 and D16 through at least one resistor. The base of transistor Q6 is also grounded through resistor R52.

[0096] Example 4 This embodiment provides a dimming method that uses the dimming power supply involved in Embodiment 1 or Embodiment 2 to dim the LED light strip, enabling rapid shutdown.

[0097] When using existing dimming power supplies to dim LED strips, the LED strip's off state is: normal off for low-brightness dimming. Specifically, after the LED strip is dimmed to low brightness and the dimming power supply is turned off, the LED strip does not immediately turn off. Instead, it first maintains a weak residual brightness, and then the brightness slowly decreases and gradually dims. The entire off process takes 1-5 seconds, with a noticeable trailing effect. The root cause is that the high-power constant voltage power supply has a built-in ultra-large filter capacitor. At low brightness, the LED strip's load power is extremely low, and the large amount of residual charge stored in the capacitor cannot be actively consumed by the LED strip. It can only rely on the LED strip's own LED beads to passively and slowly discharge until the capacitor's residual charge is exhausted and the LED strip completely turns off. In some scenarios, there will also be a slight flicker in the residual light of the LED strip, resulting in poor dimming finish, which is the most noticeable dimming defect for customers.

[0098] When the LED light strip is dimmed using the dimming power supply described in Embodiment 1 or Embodiment 2, the LED light strip can be quickly turned off. When the LED light strip is dimmed to 0.1% ultra-low brightness, the external power supply is turned off. When the external power supply is disconnected, the quick turn-off circuit cannot detect the external power supply, disconnects the power supply of the step-down chip U6, the step-down chip U6 stops working, the transformer T2 cannot perform energy conversion, and the stored electricity in the electrolytic capacitor (capacitor EC1) cannot be transferred to the LED light strip, thereby realizing the quick shutdown of the output of the dimming power supply, realizing immediate light shutdown, the LED light strip will turn off instantly, with no residual light, no brightness decay, and no trailing afterglow.

[0099] Example 4 This embodiment provides a lighting system, the light source of which includes LED light strips and downlights, and the LED light strips are dimmed using the dimming power supply involved in Embodiment 1 or Embodiment 2.

[0100] When dimming LED strips using existing dimming power supplies, the LED strip's off state is: low-brightness dimming normal off. Specifically, after the LED strip is dimmed to low brightness and the dimming power supply is turned off, the LED strip does not immediately turn off. Instead, it first maintains a weak residual brightness, and then the brightness slowly decreases and gradually dims. The entire off process takes 1-5 seconds, with a noticeable trailing phenomenon. Because LED strips are mixed with downlights, there is a serious asynchrony between the instantaneous off of the downlights and the slow, residual off of the LED strip. The human eye can clearly perceive the lag in the LED strip's off-lighting. Essentially, the high-power constant voltage power supply has a built-in ultra-large filter capacitor. When the brightness is low, the load power of the LED strip is extremely low. The large amount of residual electricity stored in the capacitor cannot be actively consumed by the LED strip. It can only rely on the LED strip beads themselves to passively and slowly discharge until the residual electricity in the capacitor is exhausted and the LED strip is completely turned off. In some scenarios, there will also be a slight flicker in the afterglow of the LED strip. The dimming finish is of poor quality, which is the dimming defect that customers perceive most strongly and is also the core complaint point in mixed installation scenarios.

[0101] When dimming an LED light strip using the dimming power supply described in Embodiment 1 or Embodiment 2, it is possible to quickly turn off the LED light strip at low brightness. Specifically: When the LED strip is adjusted to 0.1% ultra-low brightness and the external power supply is turned off, the fast shutdown circuit cannot detect the external power supply when the external power supply is disconnected, disconnecting the power supply to the step-down chip U6. The step-down chip U6 stops working, the transformer T2 cannot perform energy conversion, and the stored electricity in the electrolytic capacitor (capacitor EC1) cannot be transferred to the LED strip, thereby achieving a rapid shutdown of the dimming power supply output and immediate light shutdown. The LED strip will turn off instantly and synchronously with the downlight, with no residual light, no brightness decay, and no trailing afterglow. The entire light-off process takes a short time, and the light-off delay between the LED strip and the downlight is completely imperceptible to the naked eye, thus achieving a synchronous shutdown effect. Moreover, the low-brightness light-off effect is basically the same as the high-brightness light-off effect. The dimming end is clean and neat, which better meets the customer's demanding requirements for deep dimming.

[0102] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A dimming power supply, characterized in that, include: A fast shutdown circuit is used to detect the on / off state of the external power supply and disconnect the power supply to the buck chip when the external power supply is disconnected. The fast shutdown circuit includes an external power detection unit and a judgment output unit; The external power detection unit includes diodes D15 and D16; the positive terminals of diodes D15 and D16 are respectively connected to the live wire and neutral wire of the external power supply, and the negative terminals of diodes D15 and D16 are connected to... The judgment output unit includes transistors Q5 and Q6; the collector of transistor Q5 is connected to the power supply terminal VCC, the emitter of transistor Q5 is connected to the power supply terminal VCC1 of the step-down chip, the base of transistor Q5 is connected to the emitter of transistor Q6, the collector of transistor Q6 is grounded, and the base of transistor Q6 is connected to the negative terminal of diodes D15 and D16 through at least one resistor; the base of transistor Q6 is also grounded through resistor R52.

2. The dimming power supply according to claim 1, characterized in that, It also includes a filtering, rectification, and surge protection circuit; The filtered rectifier surge protection circuit includes: Two power input terminals, used to connect the live wire and neutral wire of an external power source, respectively; The first filtering unit uses common-mode inductors LF2 and LF3 to form a composite electromagnetic interference filtering circuit to filter noise signals. The rectifier unit uses diodes D10, D11, D12, and D13 to form a full-wave rectifier bridge, which is used to rectify AC signals into DC signals.

3. A dimming power supply according to claim 2, characterized in that, It also includes an active power factor correction boost circuit; the active power factor correction boost circuit is built based on a constant voltage control chip and is used to make the input current waveform follow the input voltage waveform and to boost the voltage. The active power factor correction boost circuit includes: The second filtering unit uses a differential-mode filter circuit composed of differential-mode inductor L1, resistor R3 and capacitor CX1 to obtain the output of the filtering rectifier surge protection circuit and suppress electromagnetic interference on the power line. The boost unit utilizes a transformer T1, a power MOSFET Q1, a diode D1, a diode D2, and a capacitor C1 to form a first power conversion circuit, which is used to boost the output of the filter unit. The boost control unit is built using a constant voltage control chip U3. By detecting the output feedback of the boost unit and sampling the current, it controls the switching frequency and duty cycle of the power MOSFET Q1.

4. A dimming power supply according to claim 3, characterized in that, It also includes a flyback buck circuit; The flyback buck circuit includes: The step-down unit utilizes transformer T2A, power MOSFET Q4, and diode D9 to form a second power conversion circuit, which is used to step down the output of the active power factor correction boost circuit. The step-down control unit, built using step-down chip U6, is used to control the switching frequency and duty cycle of the power MOSFET Q4; The first auxiliary power supply unit, consisting of transformer T2B, diodes D19, D20, D21, and transistor Q9, is used to supply power to the step-down control unit; the output VCC of the first auxiliary power supply unit is connected to the fast shutdown circuit.

5. A dimming power supply according to claim 4, characterized in that, It also includes an output rectifier circuit to rectify and filter the output of the flyback buck circuit.

6. A dimming power supply according to claim 5, characterized in that, It also includes a dimming and color-tuning circuit, which uses a power switch controller to control the duty cycle of two PWM signals.

7. A dimming power supply according to claim 6, characterized in that, It also includes an auxiliary power supply circuit, which processes the output of the output rectifier circuit to supply power to the power switch controller of the dimming and color tuning circuit.

8. A fast shutdown circuit for a dimming power supply, characterized in that, include: An external power detection unit is used to detect the on / off state of an external power supply; the external power detection unit includes diodes D15 and D16; The positive terminals of diodes D15 and D16 are connected to the live wire and neutral wire of the external power supply, respectively, and the negative terminals of diodes D15 and D16 are connected to; The output unit is used to disconnect the power supply to the step-down chip when the external power supply is disconnected. The judgment output unit includes transistors Q5 and Q6; the collector of transistor Q5 is connected to the power supply terminal VCC, the emitter of transistor Q5 is connected to the power supply terminal VCC1 of the step-down chip, the base of transistor Q5 is connected to the emitter of transistor Q6, the collector of transistor Q6 is grounded, and the base of transistor Q6 is connected to the negative terminal of diodes D15 and D16 through at least one resistor; the base of transistor Q6 is also grounded through resistor R52.

9. A dimming method, characterized in that, Dimming is performed using a dimming power supply as described in any one of claims 1-7.

10. A lighting system, the light source comprising LED light strips and downlights, characterized in that, The LED light strip is dimmed using a dimming power supply as described in any one of claims 1-7.

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