Constant-voltage auxiliary power supply circuit for LED dimming power supply

Abstract

The invention relates to the technical field of LED dimming power supplies, in particular to a constant-voltage auxiliary power supply circuit for an LED dimming power supply, and is characterized in that the primary side of a main winding of a flyback transformer T1 is coupled to the output end of a flyback module, and the secondary side of the main winding of the flyback transformer T1 is coupled to the input end of an output dimming module; an auxiliary winding TC of the flyback transformer T1 outputs electric energy, and the electric energy is rectified and filtered by the rectifying and filtering module and then respectively provides power supply voltage for the dummy load module and the step-down constant-voltage module; the voltage-reducing constant-voltage module reduces power supply voltage, generates constant voltage and transmits the constant voltage to the voltage-stabilizing module; the voltage stabilizing module is used for receiving the constant voltage and then converting the constant voltage into a preset stable voltage value; the dummy load module is used for monitoring power supply voltage, and when the power supply voltage is lower than a minimum threshold value, the dummy load module is connected to the output end of the dimming module in parallel, and the main winding feedback of the flyback transformer T1 is improved; the problems of poor insulation and unstable power supply of the auxiliary power supply in the LED dimming power supply are solved.

Description

Technical Field

[0001] This invention relates to the field of LED dimming power supply technology, and in particular to a constant voltage auxiliary power supply circuit for LED dimming power supplies. Background Technology

[0002] In LED dimming power supplies, various chips and secondary circuits (such as detection circuits) require step-down power from the main circuit. After being stepped down by the auxiliary power supply circuit, these chips and secondary circuits are powered. However, the power extraction point is usually between the flyback module and the flyback transformer in the main circuit. That is, the PFC module of the flyback circuit outputs the VBUS voltage to the primary winding of the flyback transformer. This results in a lack of basic insulation between the auxiliary power supply circuit connected to the VBUS voltage and the main circuit (i.e., the auxiliary power supply circuit is directly connected to the primary winding of the flyback transformer). Although separation can be achieved through separate grounding, isolation circuits, or the use of isolation devices, interference cannot be completely isolated. The stability of the auxiliary power supply will still be affected to some extent, especially when the main circuit dimming changes the output current, causing frequent disturbances. If a separate power supply circuit or external power supply equipment is set up, the cost will be too high. Summary of the Invention

[0003] To address the aforementioned shortcomings, the present invention aims to provide a constant voltage auxiliary power supply circuit for LED dimming power supplies, which solves the problems of poor insulation and unstable power supply in LED dimming power supplies.

[0004] To achieve this objective, the present invention adopts the following technical solution: A constant voltage auxiliary power supply circuit for LED dimming power supply includes a flyback transformer T1, a rectifier and filter module, a dummy load module, a step-down constant voltage module, and at least one type of voltage regulator module; the primary winding of the flyback transformer T1 is coupled to the output terminal of the flyback module, and the secondary winding of the flyback transformer T1 is coupled to the input terminal of the output dimming module. The electrical energy output from the auxiliary winding TC of the flyback transformer T1 is rectified and filtered by the rectifier and filter module, and then supplied to the dummy load module and the step-down constant voltage module respectively. The step-down constant voltage module steps down the power supply voltage and generates a constant voltage, which is then transmitted to the voltage regulator module. The voltage regulator module receives the constant voltage and converts it into a predetermined stable voltage value. The dummy load module is used to monitor the power supply voltage. When the power supply voltage is lower than the minimum threshold, the dummy load module is connected in parallel to the output of the dimming module to improve the feedback of the main winding of the flyback transformer T1.

[0005] Furthermore, the dummy load module includes a monitoring circuit, an optocoupler U7, a switching circuit, and a load circuit; the monitoring circuit is electrically connected to the rectifier and filter module, the monitoring circuit is electrically connected to the switching circuit via the optocoupler U7, the switching circuit is coupled to the load circuit, and the load circuit is connected in parallel to the output terminal of the dimming module; The monitoring circuit monitors the power supply voltage. When the power supply voltage is lower than the minimum threshold, the monitoring circuit activates the optocoupler U7 and the switching circuit to connect the load circuit.

[0006] Furthermore, the monitoring circuit includes resistors R62, R63, and R64, and an adjustable voltage regulator U8; one end of resistor R64 is electrically connected to the rectifier filter module, the other end of resistor R64 is electrically connected to the anode of the light source of the optocoupler U7, the cathode of the light source of the optocoupler U7 is electrically connected to the cathode of the adjustable voltage regulator U8, one end of resistor R64 is electrically connected to one end of resistor R62, the other end of resistor R62 and one end of resistor R63 are both electrically connected to the reference terminal of the adjustable voltage regulator U8, and the other end of resistor R63 and the anode of the adjustable voltage regulator U8 are both grounded.

[0007] Furthermore, the switching circuit includes resistors R65, R66, R67, R68, and R69, transistors Q5 and Q6, and a MOSFET Q7; one end of the load circuit is electrically connected to the positive terminal of the dimming module's output, the other end of the load circuit is electrically connected to the drain of the MOSFET Q7, and the source of the MOSFET Q7 is electrically connected to the negative terminal of the dimming module's output. One end of resistor R65 and the emitter of transistor Q5 are electrically connected to one end of the load circuit. The other end of resistor R65 and the base of transistor Q6 are electrically connected to the collector of the photodetector of optocoupler U7. The collector of transistor Q6 is electrically connected to the base of transistor Q5 via resistor R66. The collector of transistor Q5 and one end of resistor R68 are electrically connected to one end of resistor R67. The other end of resistor R68 and one end of resistor R69 are electrically connected to the gate of MOSFET Q7. The emitter of the photodetector of optocoupler U7, the emitter of transistor Q6, the other end of resistor R67, and the other end of resistor R69 are all electrically connected to the source of MOSFET Q7.

[0008] Furthermore, the load circuit includes at least one resistor R70; when the number of resistors R70 is one, one end of the resistor R70 is used as one end of the load circuit, and the other end of the resistor R70 is used as the other end of the load circuit. When the number of resistors R70 is greater than one, all resistors R70 are connected in parallel, and one end of the resistors R70 is connected to a common point to serve as one end of the load circuit, and the other end of the resistors R70 is connected to a common point to serve as the other end of the load circuit.

[0009] Furthermore, the step-down and constant-voltage module includes capacitor C21, diode D8, inductor L3, capacitor CE6, and step-down converter chip U9; the input terminal of the step-down converter chip U9 is electrically connected to the rectifier and filter module via its peripheral circuit, the output terminal of the step-down converter chip U9 is electrically connected to the voltage regulator module via the inductor L3, the capacitor C21 is connected in parallel between the input terminal and ground of the step-down converter chip U9, the cathode of the diode D8 is electrically connected to the common junction of the output terminal of the step-down converter chip U9 and the inductor L3, the anode of the diode D8 is grounded, the positive terminal of the capacitor CE6 is electrically connected to the common junction of the inductor L3 and the voltage regulator module, and the negative terminal of the capacitor CE6 is grounded.

[0010] Furthermore, the rectifier and filter module includes a diode D5, a capacitor CE5, and a resistor R78; the anode of the diode D5 is electrically connected to the same-name terminal of the auxiliary winding TC, the positive terminal of the capacitor CE5, one end of the resistor R78, the dummy load module, and the step-down module are all electrically connected to the cathode of the diode D5, and the negative terminal of the capacitor CE5 and the other end of the resistor R78 are all electrically connected to the opposite-name terminal of the auxiliary winding TC; The grounding of the dummy load module, the step-down module, and the detection circuit are all electrically connected to the opposite-name terminal of the auxiliary winding TC.

[0011] The technical solution provided by this invention can include the following beneficial effects: When the LED dimming power supply is working normally, the main circuit of the LED dimming power supply is: ampere block - flyback module - flyback transformer T1 - output dimming module for normal dimming output. In order to avoid interference from the main circuit (or main winding), the auxiliary power supply is selected to draw power from the auxiliary winding TC of the flyback transformer T1, and is separated from the main circuit (or main winding) to form obvious insulation separation, thereby avoiding interference from the main circuit to the auxiliary power supply circuit, and with the lowest cost.

[0012] Considering that the auxiliary winding TC will change with the voltage of the main winding, such as when the output dimming module is connected to the lamp for load dimming, it is only necessary to deal with the voltage fluctuation problem. Therefore, a step-down constant voltage module is added for voltage reduction. As long as the voltage of the main winding is not lower than the minimum threshold, the step-down constant voltage module can output a constant voltage to ensure the power supply stability of the auxiliary power supply. Thus, the various chips and secondary circuits inside the LED dimming power supply are powered by the auxiliary winding TC of the flyback transformer T1 - rectifier and filter module - step-down constant voltage module - voltage regulator module to form an auxiliary power supply circuit.

[0013] When the voltage of the main winding is lower than the minimum threshold (for example, when the LED dimming power supply is unloaded or in standby mode, the controller will turn off the dimming output of the output dimming module), that is, when the power supply voltage coupled by the auxiliary winding is lower than the minimum threshold, the dummy load module is connected in parallel to the output of the dimming module to increase the feedback of the main winding of the flyback transformer T1. This allows the flyback module connected to the primary side of the main winding of the flyback transformer T1 to know through the primary side feedback, and then the flyback module increases the voltage of the main winding to ensure that the power supply voltage recovers to above the minimum threshold, thereby ensuring the power supply stability of the auxiliary power supply. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of a constant voltage auxiliary power supply circuit for LED dimming power supply according to one embodiment of the present invention.

[0015] Figure 2 Is it like this? Figure 1 The circuit diagram of the dummy load module is shown.

[0016] Figure 3 Is it like this? Figure 1 The circuit diagram of the step-down constant voltage module is shown.

[0017] Figure 4 Is it like this? Figure 1 The circuit diagram of the voltage regulator module is shown.

[0018] The circuit consists of: flyback transformer T1, rectifier filter module 1, dummy load module 2, step-down constant voltage module 3, voltage regulator module 4, monitoring circuit 21, optocoupler U7, switching circuit 22, load circuit 23, resistors R62, R63, R64, adjustable voltage regulator U8, resistors R65, R66, R67, R68, R69, transistors Q5 and Q6, MOSFET Q7, resistor R70, capacitor C21, diode D8, inductor L3, capacitor CE6, step-down converter chip U9, diode D5, capacitor CE5, and resistor R78. Detailed Implementation

[0019] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0020] In the description of embodiments of the present invention, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the stated features. In the description of embodiments of the present invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0021] In the description of the embodiments of the present invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of the present invention according to the specific circumstances.

[0022] The following is combined with Figures 1 to 4 This invention describes a constant voltage auxiliary power supply circuit for an LED dimming power supply according to an embodiment of the present invention.

[0023] A constant voltage auxiliary power supply circuit for LED dimming power supply includes a flyback transformer T1, a rectifier and filter module 1, a dummy load module 2, a step-down constant voltage module 3, and a voltage regulator module 4 of at least one specification; the primary winding of the flyback transformer T1 is coupled to the output terminal of the flyback module, and the secondary winding of the flyback transformer T1 is coupled to the input terminal of the output dimming module 5. The electrical energy output from the auxiliary winding TC of the flyback transformer T1 is rectified and filtered by the rectifier and filter module 1, and then provides power supply voltage to the dummy load module 2 and the step-down constant voltage module 3 respectively. The step-down constant voltage module 3 steps down the power supply voltage and generates a constant voltage that is transmitted to the voltage regulator module 4. The voltage regulator module 4 receives the constant voltage and converts it into a predetermined stable voltage value. The dummy load module 2 is used to monitor the power supply voltage. When the power supply voltage is lower than the minimum threshold, the dummy load module 2 is connected in parallel to the output of the dimming module 5 to improve the feedback of the main winding of the flyback transformer T1.

[0024] In a preferred embodiment of the constant voltage auxiliary power supply circuit for LED dimming power supplies proposed in this invention, such as... Figure 1As shown, under normal operating conditions, the main circuit of the LED dimming power supply is: ampere-scale block - flyback module - flyback transformer T1 - output dimming module 5 for normal dimming output. In order to avoid interference from the main circuit (or main winding), the auxiliary power supply is selected to draw power from the auxiliary winding TC of the flyback transformer T1, which is a separate winding from the main circuit (or main winding), forming a clear insulation separation. This avoids interference from the main circuit to the auxiliary power supply circuit, and also minimizes costs.

[0025] Considering that the auxiliary winding TC will change with the voltage of the main winding, such as when the output dimming module 5 is connected to the lamp for load dimming, it is only necessary to deal with the voltage fluctuation problem. Therefore, a step-down constant voltage module 3 is added for voltage reduction. As long as the voltage of the main winding is not lower than the minimum threshold, the step-down constant voltage module 3 can output a constant voltage to ensure the power supply stability of the auxiliary power supply. Thus, the various chips and secondary circuits inside the LED dimming power supply are powered by the auxiliary winding TC of the flyback transformer T1 - rectifier filter module 1 - step-down constant voltage module 3 - voltage regulator module 4 to form an auxiliary power supply circuit.

[0026] When the voltage of the main winding is lower than the minimum threshold (for example, when the LED dimming power supply is unloaded or in standby mode, the controller will turn off the dimming output of the output dimming module 5), that is, when the power supply voltage obtained by the auxiliary winding coupling is lower than the minimum threshold, the dummy load module 2 is connected in parallel to the output terminal of the dimming module 5 to increase the feedback of the main winding of the flyback transformer T1. This allows the flyback module connected to the primary side of the main winding of the flyback transformer T1 to know through the primary side feedback, and then the flyback module increases the voltage of the main winding to ensure that the power supply voltage recovers to above the minimum threshold, thereby ensuring the power supply stability of the auxiliary power supply.

[0027] It should be noted that, based on the different requirements of various chips and secondary circuits, different specifications of voltage regulator module 4 can be selected to generate different stable voltage values, such as 3.3V, 5V, etc.; the circuit structure of voltage regulator module 4 is as follows: Figure 4 As shown, it consists of an LM1117 chip and its peripheral circuitry.

[0028] Furthermore, the dummy load module 2 includes a monitoring circuit 21, an optocoupler U7, a switching circuit 22, and a load circuit 23; the monitoring circuit 21 is electrically connected to the rectifier and filter module 1, the monitoring circuit 21 is electrically connected to the switching circuit 22 via the optocoupler U7, the switching circuit 22 is coupled to the load circuit 23, and the load circuit 23 is connected in parallel to the output terminal of the dimming module 5. The monitoring circuit 21 monitors the power supply voltage. When the power supply voltage is lower than the minimum threshold, the monitoring circuit 21 links the optocoupler U7 and the switching circuit 22, and the switching circuit 22 connects the loop of the load circuit 23.

[0029] In this embodiment, as Figure 2As shown, in the dummy load module 2, the monitoring circuit 21 is used for monitoring, the optocoupler U7 is used for isolation, the switching circuit 22 is used for switching, and the load circuit 23 is used to provide the load. Its operation can be as follows: when the monitoring circuit 21 detects that the power supply voltage is lower than the minimum threshold, the monitoring circuit 21 drives the optocoupler U7 to disconnect, causing the switching circuit 22 to conduct, thus connecting the loop of the load circuit 23. Therefore, the load circuit 23 is connected in parallel to the output terminal of the dimming module 5 to act as a lamp load.

[0030] Furthermore, the monitoring circuit 21 includes resistors R62, R63, and R64, and an adjustable voltage regulator U8; one end of resistor R64 is electrically connected to the rectifier filter module 1, the other end of resistor R64 is electrically connected to the anode of the light source of the optocoupler U7, the cathode of the light source of the optocoupler U7 is electrically connected to the cathode of the adjustable voltage regulator U8, one end of resistor R64 is electrically connected to one end of resistor R62, the other end of resistor R62 and one end of resistor R63 are both electrically connected to the reference terminal of the adjustable voltage regulator U8, and the other end of resistor R63 and the anode of the adjustable voltage regulator U8 are both grounded.

[0031] In this embodiment, the monitoring circuit 21 uses the built-in reference value of the adjustable voltage regulator U8 as the minimum threshold (the minimum threshold can be changed by selecting different specifications of the adjustable voltage regulator U8), ensuring the stability of the reference value. The voltage divider detection circuit composed of resistors R62 and R63 obtains the real-time power supply voltage and provides it to the reference terminal of the adjustable voltage regulator U8 for comparison. When the power supply voltage is normal, the power supply voltage will be greater than the reference value of the adjustable voltage regulator U8, then the adjustable voltage regulator U8 is turned on, the optocoupler U7 is turned on, and the switching circuit 22 disconnects the loop of the load circuit 23. When the power supply voltage is lower than the reference value of the adjustable voltage regulator U8, the adjustable voltage regulator U8 is turned off, the optocoupler U7 is turned off, and the switching circuit 22 connects the loop of the load circuit 23.

[0032] Furthermore, the switching circuit 22 includes resistors R65, R66, R67, R68, and R69, transistors Q5 and Q6, and MOSFET Q7; one end of the load circuit 23 is electrically connected to the positive terminal of the output of the dimming module 5, the other end of the load circuit 23 is electrically connected to the drain of the MOSFET Q7, and the source of the MOSFET Q7 is electrically connected to the negative terminal of the output of the dimming module 5. One end of resistor R65 and the emitter of transistor Q5 are electrically connected to one end of load circuit 23. The other end of resistor R65 and the base of transistor Q6 are electrically connected to the collector of the photodetector of optocoupler U7. The collector of transistor Q6 is electrically connected to the base of transistor Q5 via resistor R66. The collector of transistor Q5 and one end of resistor R68 are electrically connected to one end of resistor R67. The other end of resistor R68 and one end of resistor R69 are electrically connected to the gate of MOSFET Q7. The emitter of the photodetector of optocoupler U7, the emitter of transistor Q6, the other end of resistor R67, and the other end of resistor R69 are all electrically connected to the source of MOSFET Q7.

[0033] In this embodiment, the switching circuit 22 mainly uses MOSFET Q7 to control the connection or disconnection of the load circuit 23 loop (i.e., VIN-load circuit 23-SGND). Transistors Q5 and Q6 serve two purposes: first, to drive MOSFET Q7 based on the on / off state of optocoupler U7; second, to prevent resistor R65 from having too small a resistance value, which could cause excessive current flowing through resistor R65 and damage it. This is because if MOSFET Q7 is directly driven by resistor R65, the drive current needs to be very large, thus requiring a small resistance value for resistor R65. However, since the drive current is generated by transistors Q5 and Q6, resistor R65 does not need to be set to a very small resistance value.

[0034] The working process of the switching circuit 22 is as follows: when the optocoupler U7 is turned on, because the collector-base current of transistors Q5 and Q6 is 0, transistors Q5, Q6 and MOSFET Q7 are all turned off; otherwise, when the optocoupler U7 is turned on, transistors Q5, Q6 and MOSFET Q7 are all turned on.

[0035] Furthermore, the load circuit 23 includes at least one resistor R70; when the number of resistors R70 is one, one end of the resistor R70 is used as one end of the load circuit 23, and the other end of the resistor R70 is used as the other end of the load circuit 23. When the number of resistors R70 is greater than one, all resistors R70 are connected in parallel. One end of the resistors R70 is connected to the common point and used as one end of the load circuit 23. The other end of the resistors R70 is connected to the common point and used as the other end of the load circuit 23.

[0036] In this embodiment, the load circuit 23 is preferably composed of a single resistor R70 or multiple resistors R70 connected in parallel, and the load size can be freely adjusted so that the main winding can restore the power supply voltage to a level greater than the minimum threshold through feedback, ensuring that the voltage supplied by the voltage regulator module 4 to various chips and secondary circuits remains unchanged.

[0037] Furthermore, the step-down constant voltage module 3 includes capacitor C21, diode D8, inductor L3, capacitor CE6, and step-down converter chip U9; the input terminal of step-down converter chip U9 is electrically connected to rectifier and filter module 1 through its peripheral circuit, and the output terminal of step-down converter chip U9 is electrically connected to voltage regulator module 4 through inductor L3. Capacitor C21 is connected in parallel between the input terminal and ground terminal of step-down converter chip U9. The cathode of diode D8 is electrically connected to the common junction of the output terminal of step-down converter chip U9 and inductor L3, and the anode of diode D8 is grounded. The positive terminal of capacitor CE6 is electrically connected to the common junction of inductor L3 and voltage regulator module 4, and the negative terminal of capacitor CE6 is grounded.

[0038] In this embodiment, as Figure 3 As shown, the buck-constant voltage module 3 is a buck circuit composed of capacitor C21, diode D8, inductor L3, capacitor CE6, and buck converter chip U9. Utilizing the MOSFET integrated in the buck converter chip U9, when the MOSFET is on, the current path is: capacitor C21 - MOSFET - inductor L3 - capacitor CE6; when the MOSFET is off, the current path is: inductor L3 - capacitor CE6 - diode D8. This maintains a constant output voltage during the chopping buck process, and even if the power supply voltage received by the buck-constant voltage module 3 fluctuates within a certain range, the output voltage can remain constant.

[0039] It should be noted that the peripheral circuitry of the buck converter chip U9 can be freely constructed according to the chip datasheet and actual conditions, for example... Figure 3 The step-down converter chip U9 is an LA1821 chip, demonstrating one way to build the peripheral circuit of the LA1821 chip. Its input terminal is VIN terminal and its output terminal is SW terminal.

[0040] Furthermore, the rectifier and filter module 1 includes a diode D5, a capacitor CE5, and a resistor R78; the anode of the diode D5 is electrically connected to the same-name terminal of the auxiliary winding TC, the positive terminal of the capacitor CE5, one end of the resistor R78, the dummy load module 2, and the step-down module 3 are all electrically connected to the cathode of the diode D5, and the negative terminal of the capacitor CE5 and the other end of the resistor R78 are all electrically connected to the opposite-name terminal of the auxiliary winding TC. The grounding of the dummy load module 2, the step-down module 3, and the detection circuit 21 are all electrically connected to the opposite-named terminal of the auxiliary winding TC.

[0041] In this embodiment, diode D5 in rectifier and filter module 1 is responsible for rectification, and capacitor CE5 and resistor R78 are responsible for filtering. The rectification and filtering are performed by rectifier and filter module 1 at the beginning of the auxiliary power supply (i.e., the output of auxiliary winding TC), which eliminates the need for subsequent rectification and filtering circuits.

[0042] Other configurations and operations of a constant voltage auxiliary power supply circuit for an LED dimming power supply according to an embodiment of the present invention are known to those skilled in the art and will not be described in detail here.

[0043] In the description of this specification, references to terms such as "embodiment," "example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0044] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A constant voltage auxiliary power supply circuit for LED dimming power supplies, characterized in that: It includes a flyback transformer T1, a rectifier and filter module, a dummy load module, a step-down and constant voltage module, and at least one type of voltage regulator module; the primary winding of the flyback transformer T1 is coupled to the output terminal of the flyback module, and the secondary winding of the flyback transformer T1 is coupled to the input terminal of the output dimming module. The electrical energy output from the auxiliary winding TC of the flyback transformer T1 is rectified and filtered by the rectifier and filter module, and then supplied to the dummy load module and the step-down constant voltage module respectively. The step-down constant voltage module steps down the power supply voltage and generates a constant voltage, which is then transmitted to the voltage regulator module. The voltage regulator module receives the constant voltage and converts it into a predetermined stable voltage value. The dummy load module is used to monitor the power supply voltage. When the power supply voltage is lower than the minimum threshold, the dummy load module is connected in parallel to the output of the dimming module to improve the feedback of the main winding of the flyback transformer T1.

2. The constant voltage auxiliary power supply circuit for LED dimming power supply according to claim 1, characterized in that: The dummy load module includes a monitoring circuit, an optocoupler U7, a switching circuit, and a load circuit; the monitoring circuit is electrically connected to the rectifier and filter module, the monitoring circuit is electrically connected to the switching circuit via the optocoupler U7, the switching circuit is coupled to the load circuit, and the load circuit is connected in parallel to the output terminal of the dimming module; The monitoring circuit monitors the power supply voltage. When the power supply voltage is lower than the minimum threshold, the monitoring circuit activates the optocoupler U7 and the switching circuit to connect the load circuit.

3. The constant voltage auxiliary power supply circuit for LED dimming power supply according to claim 2, characterized in that: The monitoring circuit includes resistors R62, R63, and R64, and an adjustable voltage regulator U8. One end of resistor R64 is electrically connected to the rectifier filter module, and the other end of resistor R64 is electrically connected to the anode of the light source of the optocoupler U7. The cathode of the light source of the optocoupler U7 is electrically connected to the cathode of the adjustable voltage regulator U8. One end of resistor R64 is electrically connected to one end of resistor R62. The other ends of resistor R62 and one end of resistor R63 are both electrically connected to the reference terminal of the adjustable voltage regulator U8. The other end of resistor R63 and the anode of the adjustable voltage regulator U8 are both grounded.

4. A constant voltage auxiliary power supply circuit for LED dimming power supply according to claim 2, characterized in that: The switching circuit includes resistors R65, R66, R67, R68, and R69, transistors Q5 and Q6, and MOSFET Q7; one end of the load circuit is electrically connected to the positive terminal of the dimming module's output, the other end of the load circuit is electrically connected to the drain of MOSFET Q7, and the source of MOSFET Q7 is electrically connected to the negative terminal of the dimming module's output. One end of resistor R65 and the emitter of transistor Q5 are electrically connected to one end of the load circuit. The other end of resistor R65 and the base of transistor Q6 are electrically connected to the collector of the photodetector of optocoupler U7. The collector of transistor Q6 is electrically connected to the base of transistor Q5 via resistor R66. The collector of transistor Q5 and one end of resistor R68 are electrically connected to one end of resistor R67. The other end of resistor R68 and one end of resistor R69 are electrically connected to the gate of MOSFET Q7. The emitter of the photodetector of optocoupler U7, the emitter of transistor Q6, the other end of resistor R67, and the other end of resistor R69 are all electrically connected to the source of MOSFET Q7.

5. A constant voltage auxiliary power supply circuit for LED dimming power supply according to claim 4, characterized in that: The load circuit includes at least one resistor R70; when the number of resistors R70 is one, one end of the resistor R70 is used as one end of the load circuit, and the other end of the resistor R70 is used as the other end of the load circuit. When the number of resistors R70 is greater than one, all resistors R70 are connected in parallel, and one end of the resistors R70 is connected to a common point to serve as one end of the load circuit, and the other end of the resistors R70 is connected to a common point to serve as the other end of the load circuit.

6. A constant voltage auxiliary power supply circuit for LED dimming power supply according to claim 1, characterized in that: The step-down and constant-voltage module includes capacitor C21, diode D8, inductor L3, capacitor CE6, and step-down converter chip U9. The input terminal of the step-down converter chip U9 is electrically connected to the rectifier and filter module via its peripheral circuit. The output terminal of the step-down converter chip U9 is electrically connected to the voltage regulator module via inductor L3. Capacitor C21 is connected in parallel between the input terminal and ground of the step-down converter chip U9. The cathode of diode D8 is electrically connected to the common junction of the output terminal of the step-down converter chip U9 and the inductor L3. The anode of diode D8 is grounded. The positive terminal of capacitor CE6 is electrically connected to the common junction of the inductor L3 and the voltage regulator module. The negative terminal of capacitor CE6 is grounded.

7. A constant voltage auxiliary power supply circuit for LED dimming power supply according to claim 2, characterized in that: The rectifier and filter module includes a diode D5, a capacitor CE5, and a resistor R78. The anode of the diode D5 is electrically connected to the same-name terminal of the auxiliary winding TC. The positive terminal of the capacitor CE5, one end of the resistor R78, the dummy load module, and the step-down module are all electrically connected to the cathode of the diode D5. The negative terminal of the capacitor CE5 and the other end of the resistor R78 are all electrically connected to the opposite-name terminal of the auxiliary winding TC. The grounding of the dummy load module, the step-down module, and the detection circuit are all electrically connected to the opposite-name terminal of the auxiliary winding TC.

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