Dimming circuit, PCB and dimmable power supply

Abstract

The utility model relates to the technical field of driving power supplies, and particularly discloses a dimming circuit, a PCB and a dimmable power supply, and the dimming circuit comprises an input processing unit, a constant voltage unit, a constant current output unit, a control unit, a dial-up unit and a third transformer T3. The output end of the input processing unit is connected with the input end of the constant voltage unit and the primary coil of the third transformer T3, the output end of the constant voltage unit is connected with the primary coil of the third transformer T3, and the first secondary coil of the third transformer T3 is connected with the input end of the constant current output unit. The output end of the dial unit is connected with the detection end of the constant current output unit, and the output end of the control unit is connected with the pulse end of the constant current output unit; according to the dimming circuit disclosed by the invention, the dial unit connected with the detection end of the constant current output unit is arranged, and a user is allowed to set the output current of the dimming power supply through dial operation, so that the light brightness is accurately controlled, and the intuition and convenience of operation are ensured.

Description

Technical Field

[0001] This utility model relates to the field of driving power supply technology, and in particular to a dimming circuit, PCB board and dimmable power supply. Background Technology

[0002] A dimming power supply is a power device specifically designed to adjust the brightness of a light source. It controls the brightness of light sources such as LEDs and fluorescent lamps by changing the output current or voltage. Dimming power supplies play an important role in modern lighting systems because they not only provide a stable power supply but also allow for adjustments to the intensity of light as needed to create different atmospheres and effects.

[0003] Existing dimming power supplies have limited output current adjustment capabilities after leaving the factory. This means that once the power supply is set and installed in a specific lighting system, it is difficult for users to fine-tune or change the output current according to actual needs. This limitation may cause inconvenience to users. For example, when a specific current is needed to provide LED lights to achieve optimal brightness and color performance, a fixed-current power supply may not meet the requirements, resulting in unsatisfactory lighting effects. Secondly, the inability to adjust the current may also cause the power supply to overload in certain situations. Because it is impossible to reduce the current output according to the actual load demand, this increases the risk of damage to the power supply and the lamps. A power supply that is in an overload state for a long time may cause its internal components to age faster, shortening the overall lifespan of the dimming power supply.

[0004] It is evident that existing technologies still need improvement and enhancement. Utility Model Content

[0005] In view of the shortcomings of the prior art, the purpose of this utility model is to provide a dimming circuit that, by setting a DIP switch unit, allows users to set the output current of the dimming power supply through DIP switch operation, thereby achieving precise control of the light brightness and ensuring intuitiveness and convenience of operation.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A dimming circuit includes an input processing unit, a constant voltage unit, a constant current output unit, a control unit, a DIP switch unit, and a third transformer T3. The input terminal of the input processing unit is connected to an AC power supply terminal. The output terminal of the input processing unit is connected to both the input terminal of the constant voltage unit and the primary coil of the third transformer T3. The output terminal of the constant voltage unit is connected to the primary coil of the third transformer T3. The primary coil of the third transformer T3 is connected to the input terminal of the constant current output unit. The output terminal of the DIP switch unit is connected to the detection terminal of the constant current output unit. The input terminal of the control unit is used to acquire a dimming signal. The output terminal of the control unit is connected to the pulse terminal of the constant current output unit. The output terminal of the constant current output unit is used to connect to a lighting device.

[0008] The dimming circuit also includes a step-down unit. The secondary coil of the third transformer T3 and the output terminal of the step-down unit are connected to the power supply terminal of the control unit. The output terminal of the step-down unit is used to output a 5V DC voltage.

[0009] In the dimming circuit, the constant voltage unit includes a first control chip U1, an output adjustment unit, and an input rectifier unit; the third stage coil of the third transformer T3 is connected to the input terminal of the input rectifier unit, and the output terminal of the input rectifier unit is connected to the VCC pin of the first control chip U1; the OUT pin of the first control chip U1 is connected to the input terminal of the output adjustment unit, and the output terminal of the output adjustment unit is connected to the pin 3 of the primary coil of the third transformer T3.

[0010] In the dimming circuit, the constant voltage unit further includes a voltage detection unit and a current detection unit. The input terminal of the voltage detection unit is connected to pin 5 of the third stage coil of the third transformer T3, and the output terminal of the voltage detection unit is connected to pin FB of the first control chip U1. The input terminal of the current detection unit is connected to the output adjustment unit, and the output terminal of the current detection unit is connected to pin CS of the first control chip U1.

[0011] In the dimming circuit, the constant voltage unit further includes an active start-up unit, the output terminal of the input rectifier unit is also connected to the active start-up unit, the input terminal of the active start-up unit is connected to the input terminal of the input processing unit, and the output terminal of the active start-up unit is connected to the Vin pin of the first control chip U1.

[0012] In the dimming circuit, the constant current output unit includes an input processing unit, a fourth control chip U4, and an output processing unit. The input terminal of the input processing unit is connected to the primary winding of the third transformer T3, and the output terminal of the input processing unit is connected to the VIN pin of the fourth control chip U4. The LX pin of the fourth control chip U4 and the output terminal of the input processing unit are respectively connected to the output processing unit, and the output terminal of the output processing unit is used to connect to the lighting device. The output terminal of the DIP switch unit is connected to the CS pin of the fourth control chip U4, and the output terminal of the control unit is connected to the PWM pin of the fourth control chip U4.

[0013] In the dimming circuit, the DIP switch unit includes a DIP switch SW1 and a voltage divider. Pins 5, 6, 7 and 8 of the DIP switch SW1 are respectively connected to pin CS of the fourth control chip U4. Pins 1, 2, 3 and 4 of the DIP switch SW1 are respectively connected to pin CS of the fourth control chip U4 through the voltage divider.

[0014] In the dimming circuit, the input processing unit includes a voltage conversion section, a rectification section, and a filtering section. The input terminal of the voltage conversion section is used to connect to the AC power supply terminal. The output terminal of the voltage conversion section is connected to the power supply terminal of the control unit and the input terminal of the rectification section. The output terminal of the rectification section is connected to the input terminal of the filtering section. The output terminal of the filtering section is connected to the input terminal of the constant voltage unit and the primary coil of the third transformer T3.

[0015] This utility model also provides a PCB board, on which the dimming circuit described above is printed.

[0016] This utility model also provides a dimmable power supply, wherein the dimmable power supply uses any of the dimming circuits described above to achieve working control.

[0017] Beneficial effects:

[0018] This invention provides a dimming circuit. By setting a DIP switch unit connected to the detection terminal of the constant current output unit, the user can set the output current of the dimming power supply through DIP operation, thereby achieving precise control of the light brightness and ensuring intuitive and convenient operation. The user only needs to turn the DIP switch to adjust the output current of the dimming power supply according to personal preference or specific scene requirements, thereby changing the working state of the lighting device, improving the convenience of operation, the flexibility of the dimming power supply, and the user experience. Attached Figure Description

[0019] Figure 1 A circuit block diagram of the dimming circuit provided by this utility model;

[0020] Figure 2 The circuit diagram of the dimming circuit provided by this utility model.

[0021] Explanation of main component symbols: 1-Input processing unit, 11-Voltage conversion unit, 12-Rectifier unit, 13-Filtering unit, 2-Constant voltage unit, 21-Output adjustment unit, 22-Input rectifier unit, 23-Voltage detection unit, 24-Current detection unit, 25-Active start unit, 3-Constant current output unit, 31-Input processing unit, 32-Output processing unit, 4-Control unit, 5-DIP switch unit, 51-Voltage divider unit, 6-Voltage step-down unit. Detailed Implementation

[0022] This utility model provides a dimming circuit, a PCB board, and a dimmable power supply. To make the purpose, technical solution, and effects of this utility model clearer and more explicit, the following describes this utility model in further detail with reference to the accompanying drawings and embodiments.

[0023] In the description of this utility model, it should be understood that the terms "installation" and "connection" should be interpreted broadly, and those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0024] Please see Figure 1 and Figure 2 This utility model provides a dimming circuit, including an input processing unit 1, a constant voltage unit 2, a constant current output unit 3, a control unit 4, a DIP switch unit 5, and a third transformer T3. The input terminal of the input processing unit 1 is used to connect to an AC power supply terminal. The output terminal of the input processing unit 1 is connected to the input terminal of the constant voltage unit 2 and the primary coil of the third transformer T3. The output terminal of the constant voltage unit 2 is connected to the primary coil of the third transformer T3. The primary coil of the third transformer T3 is connected to the input terminal of the constant current output unit 3. The output terminal of the DIP switch unit 5 is connected to the detection terminal of the constant current output unit 3. The input terminal of the control unit 4 is used to acquire a dimming signal. The output terminal of the control unit 4 is connected to the pulse terminal of the constant current output unit 3. The output terminal of the constant current output unit 3 is used to connect to a lighting device.

[0025] The dimming circuit disclosed in this application, by setting a DIP switch unit 5 connected to the detection terminal of the constant current output unit 3, allows users to set the output current of the dimming power supply through DIP operation, thereby achieving precise control of the light brightness and ensuring intuitiveness and convenience of operation. Users only need to turn the DIP switch to adjust the output current of the dimming power supply according to personal preferences or specific scene requirements, thereby changing the working state of the lighting device, improving the convenience of operation, the flexibility of the dimming power supply, and the user experience.

[0026] In this embodiment, the control unit 4 is a control module U3. The control module U3 is existing technology; it only needs to be able to receive wireless dimming signals and output corresponding pulse signals. In one embodiment, it may include a control chip of model HK32F0301MF4N7C and a step-down chip of model WR0116. The control chip is used to acquire dimming signals via wireless communication and output corresponding pulse signals to the PWM pin of the fourth control chip U4 according to the received dimming signals to adjust the output current, thereby achieving dimming. The step-down chip is used to reduce the voltage to provide...

[0027] Further, please refer to Figure 1 and Figure 2 The dimming circuit also includes a step-down unit 6. The secondary coil of the third transformer T3 and the output terminal of the step-down unit 6 are connected to the power supply terminal of the control unit 4. The output terminal of the step-down unit 6 is used to output a 5V DC voltage.

[0028] In this embodiment, please refer to Figure 2 The step-down unit 6 includes a second control chip U2, which is an existing step-down chip used to step down the DC voltage received by the second stage coil of the third transformer T3 to a 5V DC voltage, so as to provide a stable operating voltage for the control unit 4; pin 2 of the second control chip U2 is connected to pin 7 of the third transformer T3, and pin 3 of the second control chip U2 is used to output a 5V DC voltage.

[0029] Further, please refer to Figure 1 and Figure 2 The constant voltage unit 2 includes a first control chip U1, an output adjustment unit 21, and an input rectifier unit 22; the third stage coil of the third transformer T3 is connected to the input terminal of the input rectifier unit 22, and the output terminal of the input rectifier unit 22 is connected to the VCC pin of the first control chip U1; the OUT pin of the first control chip U1 is connected to the input terminal of the output adjustment unit 21, and the output terminal of the output adjustment unit 21 is connected to the pin 3 of the primary coil of the third transformer T3.

[0030] In this embodiment, the first control chip U1 is model iW3627. iW3627 is a single-stage ACIDC constant voltage controller with high power factor correction. It supports various commonly used isolated and non-isolated topologies, including fyback, buck-boost, and buck. It can achieve extremely low load and line voltage regulation without secondary feedback circuitry. It also does not require external loop compensation components, ensuring stable operation under different load types and from no-load to full-load. The iW3627's adaptive output voltage limiting technology ensures transient response <10% under any load and operates in pulse frequency modulation mode under light load, thereby eliminating noise and achieving no-load standby power consumption of less than 200mW. By using the first control chip U1 of model iW3627 as the control chip of constant voltage unit 2, the overall structure of the dimming circuit can be simplified, reducing the size of the PCB board and thus the overall size of the dimming power supply.

[0031] In this embodiment, please refer to Figure 2 The output adjustment unit 21 includes a second diode D2, a twelfth resistor R12, a twenty-third resistor R23, and a first field-effect transistor Q1. The cathode of the second diode D2 is connected to pin OUT of the first control chip U1, and the anode of the second diode D2 is connected to the gate of the first field-effect transistor Q1 through the twelfth resistor R12 and the twenty-third resistor R23 connected in series. The drain of the first field-effect transistor Q1 is connected to pin 3 of the primary coil of the third transformer T3, and the source of the first field-effect transistor Q1 is grounded. By adjusting the current in the primary coil according to the change of the control signal, the first field-effect transistor Q1 affects the output voltage of the entire third transformer T3, ensuring that the output voltage remains at a constant level and remains stable even under load changes, thereby ensuring the reliability and stability of the entire dimming circuit during operation.

[0032] Further, please refer to Figure 1 and Figure 2 The constant voltage unit 2 further includes a voltage detection unit 23 and a current detection unit 24. The input terminal of the voltage detection unit 23 is connected to pin 5 of the third stage coil of the third transformer T3, and the output terminal of the voltage detection unit 23 is connected to pin FB of the first control chip U1. The input terminal of the current detection unit 24 is connected to the output adjustment unit 21, and the output terminal of the current detection unit 24 is connected to pin CS of the first control chip U1.

[0033] In this embodiment, pin FB of the first control chip U1 is a multi-function pin, which can be used to set the maximum switching frequency and enable or disable overload protection, and can also be used to provide output voltage detection for the primary-side control during normal operation; pin CS of the first control chip U1 is a multi-function pin, which is used to set the minimum switching frequency, and can also be used to provide output current detection for the primary-side control during normal operation; by setting voltage and current detection mechanisms, the dimming circuit can control the output more precisely, avoiding overload and voltage instability, thereby providing stable and reliable power support for various lighting devices, which not only improves the performance of the dimming power supply, but also enhances its safety and reliability, ensuring user safety during use and long-term stable operation of the equipment.

[0034] In this embodiment, please refer to Figure 2 The current detection unit 24 includes a ninth resistor R9 and a seventeenth resistor R17, and the voltage detection unit 23 includes an eighteenth resistor R18, a nineteenth resistor R19, and a twentieth resistor R20. One end of the ninth resistor R9 is connected to the gate of the first field-effect transistor Q1, and the other end of the ninth resistor R9 is connected to the pin CS of the first control chip U1 through the seventeenth resistor R17. One end of the eighteenth resistor R18 is connected to the pin 5 of the third stage coil of the third transformer T3, and the other end of the eighteenth resistor R18 is connected to one end of the nineteenth resistor R19. The other end of the nineteenth resistor R19 and one end of the twentieth resistor R20 are respectively connected to the pin FB of the first control chip U1, and the other end of the twentieth resistor R20 is connected to the pin Vin of the first control chip U1.

[0035] Further, please refer to Figure 1 and Figure 2 The constant voltage unit 2 further includes an active start unit 25. The output terminal of the input rectifier unit 22 is also connected to the active start unit 25. The input terminal of the active start unit 25 is connected to the input terminal of the input processing unit 1. The output terminal of the active start unit 25 is connected to the Vin pin of the first control chip U1.

[0036] In this embodiment, by setting the active start-up unit 25, the pin Vin of the first control chip U1 is equipped with an active start-up function, which can achieve the shortest start-up time without reducing efficiency, thereby significantly shortening the time required for the dimming power supply to go from standby state to full operation state and effectively improving the response speed of the dimming power supply.

[0037] In this embodiment, please refer to Figure 2The active startup unit 25 includes a second field-effect transistor Q2. The gate and drain of the second field-effect transistor Q2 are respectively connected to the output terminal of the input processing unit 1. The gate of the second field-effect transistor Q2 is also connected to the VIN pin of the first control chip U1. The source of the second field-effect transistor Q2 is grounded.

[0038] Further, please refer to Figure 1 and Figure 2 The constant current output unit 3 includes an input processing unit 31, a fourth control chip U4, and an output processing unit 32. The input terminal of the input processing unit 31 is connected to the primary winding of the third transformer T3, and the output terminal of the input processing unit 31 is connected to the VIN pin of the fourth control chip U4. The LX pin of the fourth control chip U4 and the output terminal of the input processing unit 31 are respectively connected to the output processing unit 32, and the output terminal of the output processing unit 32 is used to connect to a lighting device. The output terminal of the DIP switch unit 5 is connected to the CS pin of the fourth control chip U4, and the output terminal of the control unit 4 is connected to the PWM pin of the fourth control chip U4.

[0039] In this embodiment, the fourth control chip U4 is model FP7122. As a DC-DC asynchronous step-down constant current chip with built-in 100V, 6A, 100mΩ MOS, FP7122 can make the output current unaffected by the input and output voltages. It can achieve a conversion efficiency of 99% under full load operation and features high integration, few components, and high reliability. As an LED driver IC operating in average current mode, FP7122 does not produce peak-to-average error, thus greatly improving accuracy. LED current adjustment does not require loop compensation or high-side current detection, and it balances 3% constant current accuracy and 1% dimming depth, making it widely applicable to the driving power supply of 50W LED lighting fixtures.

[0040] In this embodiment, please refer to Figure 2The input processing unit 31 includes a fourth diode D4, a ninth diode D9, a second filter capacitor EC2, a third filter capacitor EC3, a thirty-sixth resistor R36, and a thirty-seventh resistor R37. The positive terminals of the fourth diode D4 and the ninth diode D9 are respectively connected to pin 8 of the second stage coil of the third transformer T3. The negative terminals of the fourth diode D4 and the ninth diode D9 are respectively connected to the positive terminals of the second filter capacitor EC2, the third filter capacitor EC3, one end of the thirty-sixth resistor R36, one end of the thirty-seventh resistor R37, and pin VIN of the fourth control chip U4. The negative terminals of the second filter capacitor EC2, the third filter capacitor EC3, the other end of the thirty-sixth resistor R36, and the other end of the thirty-seventh resistor R37 are respectively grounded.

[0041] In this embodiment, please refer to Figure 2 The output processing unit 32 includes a twelfth capacitor C12, a twenty-eighth resistor R28, a sixth diode D6, an eighth filter capacitor EC8, a third inductor L3, and a fourth transformer T4. One end of the twelfth capacitor C12, the negative terminal of the sixth diode D6, the positive terminal of the eighth filter capacitor EC8, and one end of the fourth transformer T4 are respectively connected to one end of the thirty-seventh resistor R37. The other end of the twelfth capacitor C12 is connected to one end of the twenty-eighth resistor R28. The other end of the twenty-eighth resistor R28, the positive terminal of the sixth diode D6, and the LX pin of the fourth control chip U4 are respectively connected to one end of the third inductor L3. The other end of the third inductor L3 and the negative terminal of the eighth filter capacitor EC8 are respectively connected to one end of the fourth transformer T4. The other end of the fourth transformer T4 is used to connect to a lighting device.

[0042] Further, please refer to Figure 1 and Figure 2 The DIP switch unit 5 includes a DIP switch SW1 and a voltage divider 51. Pins 5, 6, 7 and 8 of the DIP switch SW1 are respectively connected to pins CS of the fourth control chip U4. Pins 1, 2, 3 and 4 of the DIP switch SW1 are respectively connected to pins CS of the fourth control chip U4 through the voltage divider 51.

[0043] In this embodiment, the voltage divider 51 is composed of multiple voltage divider resistors. By adjusting the switching state of the DIP switch SW1, the conduction state of the corresponding voltage divider resistors can be adjusted. That is, by toggling the switch, certain resistors can be selectively included in the circuit or excluded from the circuit. This adjustment directly affects the current path flowing through the voltage divider 51, thereby changing the total resistance of the resistor network. As the total resistance changes, the voltage on pin CS of the fourth control chip U4 will also change accordingly, thereby changing the magnitude of the output current to meet different application requirements.

[0044] Further, please refer to Figure 1 and Figure 2 The input processing unit 1 includes a voltage conversion unit 11, a rectifier unit 12, and a filter unit 13. The input terminal of the voltage conversion unit 11 is used to connect to the AC power supply terminal. The output terminal of the voltage conversion unit 11 is connected to the power supply terminal of the control unit 4 and the input terminal of the rectifier unit 12, respectively. The output terminal of the rectifier unit 12 is connected to the input terminal of the filter unit 13, and the output terminal of the filter unit 13 is connected to the input terminal of the constant voltage unit 2 and the primary coil of the third transformer T3, respectively.

[0045] In this embodiment, please refer to Figure 2 The voltage conversion unit 11 includes a first transformer T1 and a second transformer T2; the rectifier unit 12 includes a rectifier bridge DB1; and the filter unit 13 includes a second inductor L2, a first resistor R1, a first capacitor C1, a second capacitor C2, and a second adjustable resistor VR2. One end of the first transformer T1 is connected to an AC power supply device, which can be AC ​​mains power. The other end of the first transformer T1 is connected to one end of the second transformer T2. The other end of the second transformer T2 is connected to the power supply terminal of the control unit 4 and any two pins of the rectifier bridge DB1. The other pin of the rectifier bridge DB1 is connected to one end of the first capacitor C1, one end of the second inductor L2, and one end of the first resistor R1. The other end of the second inductor L2 and the other end of the first resistor R1 are connected to one end of the second capacitor C2, one end of the second adjustable resistor VR2, and the gate of the second field-effect transistor Q2, respectively. The other ends of the first capacitor C1, the second capacitor C2, and the second adjustable resistor VR2 are grounded.

[0046] This utility model also provides a PCB board, on which the dimming circuit described above is printed.

[0047] This utility model also provides a dimmable power supply, wherein the dimmable power supply uses any of the dimming circuits described above to achieve working control.

[0048] It is understood that those skilled in the art can make equivalent substitutions or changes based on the technical solution and inventive concept of this utility model, and all such substitutions or changes should fall within the protection scope of this utility model.

Claims

1. A dimming circuit, characterized in that, The system includes an input processing unit, a constant voltage unit, a constant current output unit, a control unit, a DIP switch unit, and a third transformer T3. The input terminal of the input processing unit is connected to an AC power supply terminal. The output terminal of the input processing unit is connected to the input terminal of the constant voltage unit and the primary coil of the third transformer T3. The output terminal of the constant voltage unit is connected to the primary coil of the third transformer T3. The primary coil of the third transformer T3 is connected to the input terminal of the constant current output unit. The output terminal of the DIP switch unit is connected to the detection terminal of the constant current output unit. The input terminal of the control unit is used to acquire a dimming signal. The output terminal of the control unit is connected to the pulse terminal of the constant current output unit. The output terminal of the constant current output unit is used to connect to a lighting device.

2. The dimming circuit according to claim 1, characterized in that, It also includes a step-down unit, the secondary coil of the third transformer T3 is connected to the output terminal of the step-down unit and the power supply terminal of the control unit, and the output terminal of the step-down unit is used to output a 5V DC voltage.

3. The dimming circuit according to claim 1, characterized in that, The constant voltage unit includes a first control chip U1, an output adjustment section, and an input rectification section; the third stage coil of the third transformer T3 is connected to the input terminal of the input rectification section, and the output terminal of the input rectification section is connected to the VCC pin of the first control chip U1; the OUT pin of the first control chip U1 is connected to the input terminal of the output adjustment section, and the output terminal of the output adjustment section is connected to the pin 3 of the primary coil of the third transformer T3.

4. A dimming circuit according to claim 3, characterized in that, The constant voltage unit further includes a voltage detection unit and a current detection unit. The input terminal of the voltage detection unit is connected to pin 5 of the third stage coil of the third transformer T3, and the output terminal of the voltage detection unit is connected to pin FB of the first control chip U1. The input terminal of the current detection unit is connected to the output adjustment unit, and the output terminal of the current detection unit is connected to pin CS of the first control chip U1.

5. A dimming circuit according to claim 3, characterized in that, The constant voltage unit also includes an active start unit. The output terminal of the input rectifier unit is also connected to the active start unit. The input terminal of the active start unit is connected to the input terminal of the input processing unit. The output terminal of the active start unit is connected to the Vin pin of the first control chip U1.

6. A dimming circuit according to claim 1, characterized in that, The constant current output unit includes an input processing unit, a fourth control chip U4, and an output processing unit. The input terminal of the input processing unit is connected to the primary winding of the third transformer T3, and the output terminal of the input processing unit is connected to the VIN pin of the fourth control chip U4. The LX pin of the fourth control chip U4 and the output terminal of the input processing unit are respectively connected to the output processing unit, and the output terminal of the output processing unit is used to connect to a lighting device. The output terminal of the DIP switch unit is connected to the CS pin of the fourth control chip U4, and the output terminal of the control unit is connected to the PWM pin of the fourth control chip U4.

7. A dimming circuit according to claim 6, characterized in that, The DIP switch unit includes a DIP switch SW1 and a voltage divider. Pins 5, 6, 7 and 8 of the DIP switch SW1 are respectively connected to pin CS of the fourth control chip U4. Pins 1, 2, 3 and 4 of the DIP switch SW1 are respectively connected to pin CS of the fourth control chip U4 through the voltage divider.

8. A dimming circuit according to claim 1, characterized in that, The input processing unit includes a voltage conversion section, a rectification section, and a filtering section. The input terminal of the voltage conversion section is used to connect to the AC power supply terminal. The output terminal of the voltage conversion section is connected to the power supply terminal of the control unit and the input terminal of the rectification section. The output terminal of the rectification section is connected to the input terminal of the filtering section. The output terminal of the filtering section is connected to the input terminal of the constant voltage unit and the primary coil of the third transformer T3.

9. A PCB board, characterized in that, The PCB board is printed with a dimming circuit as described in any one of claims 1-8.

10. A dimmable power supply, characterized in that, The dimmable power supply uses the dimming circuit described in any one of claims 1-8 to achieve operation control.

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