LED street lamp digital intelligent dimming high-efficiency switching power supply and control method thereof

Abstract

The application discloses an LED street lamp digital intelligent dimming high-efficiency switching power supply and a control method thereof. Two-way active power factor correction boost circuits and two-way switching conversion circuits are adopted to work cooperatively. The first switching conversion circuit undertakes main output when the dimming duty cycle D is greater than or equal to 50% and undertakes auxiliary output when the dimming duty cycle D is less than 50%. The second switching conversion circuit undertakes main output when the dimming duty cycle D is less than 50% and undertakes auxiliary output when the dimming duty cycle D is greater than or equal to 50%. An MCU digital control unit detects current, voltage and a target dimming duty cycle in real time, dynamically calculates and adjusts two-way output power distribution ratios K1 and K2, so that the circuit undertaking main output always works in an optimal efficiency interval. Meanwhile, low-resistance silicon carbide switching tubes, special gate drivers and synchronous rectification circuits and other high-efficiency power devices are adopted, so that the technical problem of a sharp decrease in efficiency of a traditional dimming power supply after dimming is solved, and the energy-saving benefit of a street lamp energy-saving reconstruction project is remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of LED lighting driver power supply technology, specifically to a digital intelligent dimming high-efficiency switching power supply for street lighting, and more particularly to an LED dimming power supply and its control method that achieves high-efficiency output across the entire dimming range by working in conjunction with a dual-channel active power factor correction circuit and a dual-channel switching conversion circuit. Background Technology

[0002] LED lighting, with its energy-saving, environmentally friendly, and long-life characteristics, has become a globally recognized third-generation light source, widely used in road lighting, landscape lighting, and other fields. LED street light energy-saving retrofit projects have become an important part of urban lighting upgrades. Statistics show that the global total number of streetlights exceeds 300 million, with approximately 30 million in China, and this number is growing at a rate of about 10% annually.

[0003] In LED street light driver power supplies, dimming is a crucial means of achieving secondary energy savings—reducing street light brightness when traffic decreases in the latter half of the night can further conserve energy. However, existing LED dimming power supplies face a long-standing technical challenge: while the power supply efficiency is typically rated at 85%-94% at peak output, it significantly decreases as the dimming depth increases (output power decreases), with the efficiency dropping even more as the dimming level rises. The root cause of this problem lies in: First, the switching losses of traditional single-channel switching circuits increase sharply under light load conditions, leading to a significant drop in efficiency. Taking a typical Buck-Boost topology as an example, when the load decreases from 100% to 10%, the switching losses can increase from 30% to over 65% of the total losses.

[0004] Second, power factor correction (PFC) circuits struggle to maintain high efficiency under light loads. Under light loads (such as less than 20% power), BoostPFC circuits experience a significant increase in conduction losses and losses in critical conduction mode (DCM) due to increased input current ripple, reduced switching frequency, and higher input current ripple.

[0005] Third, existing dimming solutions lack an adaptive optimization mechanism for dual-path power distribution. Most solutions use a single main output plus a secondary standby output, or simple parallel current sharing, which cannot dynamically allocate more power to the circuit in its optimal efficiency range according to the dimming depth.

[0006] Furthermore, existing dual-output LED power supply solutions mostly focus on achieving dual-channel constant current output or dimming functionality, but lack specific design for efficiency optimization across the entire dimming range. Typical defects include: fixed power distribution between the two outputs (e.g., 5:5 or 6:4), without dynamic adjustment based on dimming depth, resulting in extremely low efficiency for one output under light load; insufficient precision in the control chip, with PWM resolution typically at 8 bits (256 levels), making it impossible to precisely control the power distribution between the two outputs across the entire dimming range, leading to efficiency fluctuations; lack of efficient gate drive design for silicon carbide (SiC) devices, failing to fully leverage the advantages of SiC MOSFETs; and inadequate matching design between the synchronous rectification controller and the MOSFETs, resulting in a high proportion of rectification losses (reaching 15%-25% of total losses).

[0007] Therefore, developing an LED dimming power supply that can maintain high-efficiency output across the entire dimming range of 0-100% is of significant practical importance and economic value for street light energy-saving renovation projects. Summary of the Invention

[0008] This invention addresses the technical deficiency of existing LED dimming power supplies, which result in a significant drop in efficiency after dimming. It provides a high-efficiency digital intelligent dimming switching power supply for LED streetlights and its control method, aiming to achieve high-efficiency output across the entire dimming range of 0-100%, ensuring that the power supply efficiency remains at a high level even as the dimming depth increases, thereby bringing more energy-saving benefits to streetlight energy-saving renovation projects.

[0009] To achieve the above objectives, the present invention provides a high-efficiency digital intelligent dimming switching power supply for LED streetlights, comprising: Two independent active power factor correction (PFC) boost circuits are used to rectify and correct the power factor of the input AC power and output two DC bus voltages. Two independent switching conversion circuits are respectively connected to the output terminals of the two PFC boost circuits, and are used to convert the DC bus voltage into the driving voltage required by the LED load; A synchronous rectification and filtering circuit is connected to the output terminals of the two switching circuits respectively, and is used to synchronously rectify and filter the outputs of the two switching circuits; The output merging circuit is connected to the output terminals of the two synchronous rectification and filtering circuits, and is used to combine the two outputs to supply the LED load. The current detection circuit, voltage detection circuit, and dimming signal input interface are used to detect the output current and output voltage respectively and to receive external dimming commands. An MCU digital control unit is connected to the control terminals of the current detection circuit, voltage detection circuit, dimming signal input interface, two PFC boost circuits, and two switching circuits.

[0010] This invention employs a power allocation strategy of primary and secondary circuitry with dynamic switching: at any dimming depth, the circuit responsible for the main output always operates within its optimal efficiency range, while the other circuit operates only under light load or auxiliary conditions. A typical allocation is shown in the table below:

[0011] The above data is based on the measured efficiency curves of the actual test platform, showing that the efficiency fluctuation of the present invention is less than 2 percentage points (82%-97.2%) across the entire dimming range, while the efficiency of traditional dimming power supplies has dropped to below 75% at 10% brightness.

[0012] Preferably, the MCU digital control unit compares the target dimming duty cycle D with a preset threshold (50%): when D ≥ 50%, the first switching circuit is configured to handle the main output and the second switching circuit to handle the auxiliary output; when D < 50%, the second switching circuit is configured to handle the main output and the first switching circuit to handle the auxiliary output. Simultaneously, the MCU digital control unit calculates the output power allocation ratios K1 and K2 (K1 + K2 = 1) of the two switching circuits in real time based on the detected current, voltage, and target dimming duty cycle D, and adjusts the operating parameters of the two switching circuits and the corresponding PFC boost circuits accordingly, ensuring that the switching circuit handling the main output always operates within its optimal efficiency range. Specifically, the MCU digital control unit monitors the following key parameters in real time and, based on a preset efficiency-power curve, dynamically calculates the optimal output power allocation ratio of the two switching circuits through closed-loop control: Output current value: sampled by a precision current sensing resistor (e.g., 0.001Ω, 0.1% accuracy) in conjunction with an instrumentation amplifier, ADC resolution 12 bits; Output voltage value: sampled by a resistor divider network (e.g., 100kΩ / 10kΩ), ADC resolution 12 bits; Input dimming PWM duty cycle signal: fed into the MCU's capture / compare unit (TIM) after high-frequency filtering and comparator shaping; Bus voltage and temperature: monitored by voltage divider sampling of the DC bus voltage and by NTC thermistor monitoring of the junction temperature of key components to achieve over-temperature protection. The MCU dynamically calculates the two output power allocation ratios K1 and K2 (K1+K2=1) according to a preset efficiency optimization algorithm, ensuring that both circuits operate within their respective optimal efficiency ranges at any dimming depth. The core formula of the control algorithm is as follows: When D ≥ 50%: K1 = 0.5 + 0.8 × (D − 50%) / 50%, K2 = 1 − K1; When D < 50%: K2 = 0.5 + 0.8 × (50% − D) / 50%, K1 = 1 − K2. Where D is the dimming duty cycle (0% ≤ D ≤ 100%), K1 is the power allocation ratio for the first path, and K2 is the power allocation ratio for the second path. The coefficient 0.8 ensures that even at the extreme dimming depth, the main path still has sufficient power margin to maintain its optimal efficiency operating range (load rate not less than 15%).

[0013] Preferably, the switching conversion circuit adopts an LLC resonant converter topology and is controlled by an LLC resonant controller, which is one of the NCP13992, ICL5102, or MP4655 series chips; the active power factor correction boost circuit adopts a Boost topology and is controlled by a PFC controller, which is one of the BP2628, LM3447, TPS92075, or ICL5102 series chips; the main switching transistor of the switching conversion circuit is a silicon carbide MOSFET, and the switching conversion circuit is also equipped with a dedicated gate driver to drive the silicon carbide MOSFET. The gate drive voltage of the gate driver is +15V to ensure that the silicon carbide device operates in the saturation region and minimizes conduction losses.

[0014] Preferably, the synchronous rectification and filtering circuit includes a synchronous rectification controller and a synchronous rectification MOSFET driven by the synchronous rectification controller. The synchronous rectification controller detects the current direction of the output inductor of the switching circuit and controls the synchronous rectification MOSFET to conduct during the freewheeling current of the inductor.

[0015] Preferably, the MCU digital control unit is a 32-bit microcontroller with a PWM output resolution of no less than 16 bits, which can finely control the power distribution of the two channels; the dimming signal input interface supports both PWM dimming signals and 0-10V analog dimming signals, and is equipped with an automatic identification circuit that automatically switches the working mode according to the type of input signal. When the junction temperature of the power device in any switching circuit exceeds a preset threshold, the MCU digital control unit automatically shifts the power distribution ratio of that channel to the other channel by a preset ratio to balance the heat load of the two channels.

[0016] Preferably, the output merging circuit uses a MOSFET switch in conjunction with a logic control circuit to achieve conflict-free merging of the two outputs. At any given time, only one output of the synchronous rectification and filtering circuit is allowed to be connected to the LED load, thus avoiding short circuit between the two outputs.

[0017] Preferably, the power supply has an average conversion efficiency of not less than 97% and a peak efficiency of not less than 98.5% in the full dimming range of 0-100%; and a conversion efficiency of not less than 94% when the dimming duty cycle is less than 30%.

[0018] This invention also discloses a control method for the high-efficiency digital intelligent dimming switching power supply for LED streetlights as described above, comprising the following steps: S1: The MCU digital control unit is powered on, initialized, and performs a self-test, reading the preset efficiency-power curve parameters; S2: The MCU digital control unit reads external dimming commands through the dimming signal input interface to obtain the target dimming duty cycle D, where 0%≤D≤100%; S3: The MCU digital control unit detects the output current Iout and output voltage Vout in real time through the current detection circuit and voltage detection circuit, and calculates the current output power Pout=Iout×Vout; S4: The MCU digital control unit determines the main and auxiliary circuits based on the comparison between the target dimming duty cycle D and the preset threshold: when D≥50%, the first switching circuit is the main circuit and the second switching circuit is the auxiliary circuit; when D<50%, the second switching circuit is the main circuit and the first switching circuit is the auxiliary circuit; and calculates the first output power allocation ratio K1 and the second output power allocation ratio K2 according to the preset efficiency optimization algorithm, K1+K2=1; S5: The MCU digital control unit calculates and outputs the control parameters of the two switching circuits according to K1 and K2 respectively, and dynamically adjusts the boost ratio of the two active power factor correction boost circuits. S6: The MCU digital control unit continuously monitors the output parameters and uses a PID closed-loop control algorithm to adjust the control quantity so that the output power follows the target dimming duty cycle D. When the junction temperature of the power device is detected to exceed the preset threshold, the power allocation ratio of that channel is automatically reduced. S7: Repeat steps S2 to S6 to achieve real-time dynamic optimization control.

[0019] Preferably, the power allocation ratio in step S4 is calculated as follows: when D ≥ 50%, K1 = 0.5 + 0.8 × (D - 50%) / 50%, K2 = 1 - K1; when D < 50%, K2 = 0.5 + 0.8 × (50% - D) / 50%, K1 = 1 - K2; where the coefficient 0.8 ensures that the switching circuit that bears the main output still maintains a load rate of not less than 15% under the extreme dimming depth.

[0020] Preferably, the control parameter in step S5 is the PWM duty cycle or switching frequency, and the two switching circuits adjust their respective output power by changing the PWM duty cycle or switching frequency.

[0021] Preferably, a remote monitoring step is also included: the MCU digital control unit uploads the operating parameters to the monitoring platform via UART or CAN interface, and supports online firmware upgrades.

[0022] Compared with the prior art, the present invention has the following beneficial technical effects: (1) Two independent active power factor correction boost circuits and two independent switching conversion circuits work together. The MCU digital control unit compares the target dimming duty cycle D with the preset threshold (50%). When D≥50%, the first path is configured as the main path and the second path as the auxiliary path. When D<50%, the second path is configured as the main path and the first path as the auxiliary path. This solves the technical problems of the traditional single-path switching conversion circuit, which suffers a sharp drop in efficiency due to the increase in the proportion of switching loss under light load conditions, and the traditional dual-path scheme, which uses fixed power allocation, resulting in extremely low efficiency of one path under light load conditions. It has the technical effect of realizing the division of labor between the main and auxiliary paths and dynamic switching in the entire dimming range, ensuring that the circuit that undertakes the main output always works in its optimal efficiency range, and effectively avoiding the efficiency collapse of a single path under light load conditions. (2) The MCU digital control unit is used to detect the output current, output voltage and target dimming duty cycle D in real time. The power distribution ratios K1 and K2 (K1+K2=1) of the two outputs are dynamically calculated according to the preset efficiency optimization algorithm. A 32-bit microcontroller with a PWM output resolution of not less than 16 bits is used. The control quantity is continuously adjusted and the boost ratio of the two PFC boost circuits is dynamically adjusted through the PID closed-loop control algorithm. This solves the technical problems of traditional dimming power supplies being unable to finely control the power distribution of the two outputs in the full dimming range, resulting in large efficiency fluctuations, and the traditional solution having a PWM resolution of only 8 bits, which cannot meet the requirements of fine dimming control. It has the technical effect of achieving an extremely flat efficiency curve in the full dimming range, efficiency fluctuation of less than 2 percentage points, average conversion efficiency of not less than 97%, peak efficiency of not less than 98.5%, and efficiency of not less than 94% when the dimming duty cycle is less than 30%. (3) The main switching transistor of the switching conversion circuit uses a low internal resistance silicon carbide MOSFET and is equipped with a dedicated gate driver with a gate drive voltage of +15V. The synchronous rectification and filtering circuit includes a synchronous rectification controller and a synchronous rectification MOSFET. The synchronous rectification controller detects the current direction of the output inductor of the switching conversion circuit and controls the synchronous rectification MOSFET to conduct during the inductor current freewheeling period. This solves the technical problems of high switching and conduction losses when using silicon-based power devices, high rectifier losses in traditional diode rectification methods accounting for 15%-25% of the total losses, and the failure to fully utilize the advantages of silicon carbide devices due to improper gate drive design. It has the technical effects of minimizing switching and conduction losses, providing key hardware support for peak efficiency of over 98.5%, and reducing thermal stress of power devices to extend power supply life. (4) The MCU digital control unit automatically transfers the power distribution ratio of the circuit to the other circuit by a preset ratio when the junction temperature of the power device in any switching circuit exceeds the preset threshold in order to balance the heat load of the two circuits. This solves the technical problems of high power density, heat stress concentration leading to excessively high junction temperature of the device and shortened power supply life in traditional single power supply, as well as the problem that uneven power distribution in dual-circuit scheme may cause overheating of a certain circuit. It has the technical effects of lower junction temperature of device in dual-circuit scheme than single-circuit scheme under the same heat dissipation conditions, extended service life by more than 30%, avoiding system derating or protection shutdown due to heat concentration, and improving system reliability and long-term operation stability. (5) By adopting built-in overvoltage protection, overcurrent protection, overtemperature protection, short circuit protection and input undervoltage lockout, as well as the MCU digital control unit uploading working parameters to the monitoring platform through UART or CAN interface and supporting online firmware upgrade, the technical means are used to solve the problems of traditional power supplies being easily damaged due to lack of comprehensive protection under abnormal working conditions, as well as the high operation and maintenance costs of traditional power supplies and the inability to remotely monitor and update firmware. It has the technical effects of ensuring the safe and reliable operation of the system under various abnormal conditions, reducing operation and maintenance costs, supporting intelligent operation and maintenance management, extending the service life of the power supply and improving the maintainability of the system. (6) The dimming signal input interface supports both PWM dimming signal and 0-10V analog dimming signal input and is equipped with an automatic identification circuit to automatically switch the working mode according to the input signal type. It also has two active PFC boost circuits to rectify and correct the power factor of the input AC power. This solves the technical problems of poor compatibility of traditional dimming power supplies, which can only support a single dimming protocol, as well as the low power factor, high total harmonic distortion, and the need to add an additional filter. It has the technical effects of being able to be easily connected to existing lighting control systems such as DALI and ZMUX, having a full-range power factor ≥0.97, total harmonic distortion ≤5%, meeting the limit requirements of EN61000-3-2 and GB17625.1, not requiring an additional filter, and further reducing the system cost and size. By comprehensively utilizing all the aforementioned technologies, including dual-path dynamic allocation, high-efficiency power devices, precise control, thermal balance protection, comprehensive protection functions, remote monitoring, good compatibility, and high power factor, this technology solves the technical problem that the efficiency of traditional dimming power supplies drops significantly as dimming depth increases, resulting in a substantial reduction in secondary energy-saving effects. Taking a typical 150W LED street light as an example, it can reduce the total daily power consumption by approximately 23.1Wh, save approximately 8.4kWh of electricity per lamp per year, significantly improve the energy-saving benefits of street light energy-saving renovation projects, and has significant practical significance and economic value. Attached Figure Description

[0023] Figure 1 This is a flowchart illustrating the control method for the high-efficiency switching power supply of the present invention. Detailed Implementation

[0024] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. However, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Example 1

[0025] Please see Figure 1 This embodiment discloses a high-efficiency switching power supply for digital intelligent dimming of LED streetlights with a rated power of 150W, which is the core embodiment of the present invention. The main technical parameters are as follows:

[0026] Key component selection details:

[0027] The circuit connection relationship in this embodiment is as follows: AC Input Side: AC Mains (AC L / N) → EMI Filter Circuit (Common Mode Inductor CM100-2-240 plus X2 Capacitors 0.22μF / 275VAC plus Y1 Capacitors 2200pF×2) → Rectifier Bridge Circuit (GBU806, 6A / 800V) → DC Bus (DCBus, approximately 90-380V).

[0028] PFC Stage: The DC bus is connected to the first and second PFC boost circuits respectively. Both PFC circuits adopt a Boost topology and are controlled by a PFC controller (such as BP2628), outputting a stable high-voltage DC bus (approximately 380-400V). Each PFC circuit includes: input inductors (L1 / L2, such as Wurth WE-P698 series, 2.2μH / 20A), a power MOSFET (SiC, C3M0120065D), and output capacitors (two 470μF / 400V electrolytic capacitors in parallel). The outputs of the two PFC circuits are filtered by their respective bus capacitors before being sent to the corresponding switching circuits.

[0029] Switching stage: First PFC output → First switching circuit (including LLC resonant converter, controlled by NCP13992) → First synchronous rectification and filtering circuit; Second PFC output → Second switching circuit (including LLC resonant converter, controlled by NCP13992) → Second synchronous rectification and filtering circuit.

[0030] The main parameters of each LLC resonant converter are: resonant inductance Lr = 100μH, resonant capacitor Cr = 0.47μF (two 0.22μF capacitors in series), transformer T (turns ratio 1:12, magnetic core PM3210+, Ae = 148mm²), and secondary output inductance Lf = 470μH. The LLC controller has a frequency modulation range of 100kHz-500kHz, and the frequency is controlled by detecting the zero-crossing signal of the secondary current. The main switching transistors of both switching circuits are silicon carbide MOSFETs (C3M0120065D), driven by LM5109B gate drivers with a gate drive voltage of +15V.

[0031] Control Level: The ADC channels 0-3 of the MCU (HK32F103CBT6) are connected to: the output current sampling circuit (0.001Ω precision resistor plus instrumentation amplifier ADA4523-1), the output voltage sampling circuit (100kΩ / 10kΩ voltage divider network), the bus voltage sampling circuit, and the thermistor sampling circuit, respectively. The MCU's timer channels (TIM1 / 2 / 3) generate 16-bit high-precision PWM signals, which are connected to the PWM input pins of the two LLC controllers, respectively. Independent control of the two output power is achieved by adjusting the PWM duty cycle or frequency. The MCU also reserves remote monitoring and firmware upgrade functions through the UART interface.

[0032] Output stage: The outputs of the two synchronous rectification and filtering circuits are connected to the output merging circuit. The merging circuit uses two MOSFETs (SI4435DV) as synchronous rectification switches, and works with logic control circuits to ensure proper merging of the two outputs (avoiding short circuits). The merged output is then filtered by output filter capacitors (two 470μF / 35V electrolytic capacitors in parallel) before being connected to the LED load. Example 2

[0033] A high-efficiency switching power supply with digital intelligent dimming for LED streetlights, rated at 300W, is suitable for high-power LED streetlight modules (such as 200W-400W LED streetlights). Its main technical parameters are as follows:

[0034] This embodiment uses the ICL5102 integrated PFC and LLC combination control chip, which completes dual-function control of one PFC and one LLC with a single chip, saving PCB area. The rest of the structure is the same as in embodiment 1, and will not be described again here. Example 3

[0035] Please see Figure 1 To better understand the control method of this invention, the specific implementation parameters of the MCU control algorithm are given below: PWM frequency: The main PWM frequency is set to 500Hz (flicker invisible to the human eye), and the PWM resolution is 16-bit (with a step of approximately 0.008% dimming depth).

[0036] LLC frequency modulation: Power regulation is achieved through internal frequency modulation of the LLC controller, with a modulation range of 100kHz-500kHz. The frequency is inversely proportional to the output power.

[0037] PFC boost ratio control: dynamically adjusts the PFC output target voltage according to load requirements (fine-tuning within the range of 380V-400V) to optimize PFC efficiency.

[0038] Temperature compensation: When the junction temperature of any power device is detected to exceed 85°C, the power distribution will be automatically shifted to another path by 5%-10% to avoid heat concentration.

[0039] Sleep mode: When the dimming command is 0% for more than 5 minutes, the system will automatically enter the ultra-low power standby mode (standby power consumption <0.5W), and the LED will be completely turned off.

[0040] The control method of the present invention includes the following steps: S1: The MCU digital control unit is powered on and initialized and performs a self-test, including ADC calibration, PWM channel configuration, communication interface initialization, and reading the preset efficiency-power curve parameter table stored in Flash.

[0041] S2: The MCU digital control unit reads external dimming commands through the dimming signal input interface (supports PWM and 0-10V analog signals, which are identified by an automatic identification circuit) to obtain the target dimming duty cycle D (0%≤D≤100%).

[0042] S3: The MCU digital control unit detects the output current Iout and output voltage Vout in real time through the current sampling circuit and voltage sampling circuit, and calculates the current output power Pout=Iout×Vout.

[0043] S4: The MCU digital control unit calculates the first output power allocation ratio K1 and the second output power allocation ratio K2 (K1+K2=1) according to the target dimming duty cycle D and the current output power Pout, based on the preset efficiency optimization algorithm: When D≥50%, K1=0.5+0.8×(D-50%) / 50%, K2=1-K1, and the first channel undertakes the main output; when D<50%, K2=0.5+0.8×(50%-D) / 50%, K1=1-K2, and the second channel undertakes the main output.

[0044] S5: The MCU digital control unit calculates the control parameters (PWM duty cycle or switching frequency) of the two switching circuits according to K1 and K2 respectively, and controls the first switching circuit and the second switching circuit respectively through the PWM output port; at the same time, it dynamically adjusts the boost ratio of the two PFCs according to the K value.

[0045] S6: The MCU digital control unit continuously monitors output parameters (current, voltage, temperature, duty cycle) and uses a PID closed-loop control algorithm to adjust the control input, ensuring that the output power accurately follows the dimming command, while both circuits operate within their optimal efficiency range. If the temperature of a device exceeds a threshold (e.g., 100℃), the power allocation ratio for that circuit is automatically reduced.

[0046] S7: Repeat steps S2 to S6 to achieve real-time dynamic optimization control. The system performs approximately 200 power allocation optimization cycles per second to ensure optimal efficiency while responding to changes in dimming commands.

[0047] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A high-efficiency switching power supply for digital intelligent dimming of LED streetlights, characterized in that, include: Two independent active power factor correction boost circuits are used to rectify and correct the power factor of the input AC power and output two DC bus voltages. Two independent switching conversion circuits are respectively connected to the output terminals of the two active power factor correction boost circuits, and are used to convert the DC bus voltage into the driving voltage required by the LED load; A synchronous rectification and filtering circuit is connected to the output terminals of the two switching circuits respectively, and is used to synchronously rectify and filter the outputs of the two switching circuits; The output merging circuit is connected to the output terminals of the two synchronous rectification and filtering circuits, and is used to combine the two outputs to supply the LED load. The current detection circuit, voltage detection circuit, and dimming signal input interface are used to detect the output current and output voltage respectively and to receive external dimming commands. An MCU digital control unit is connected to the control terminals of the current detection circuit, voltage detection circuit, dimming signal input interface, two active power factor correction boost circuits, and two switching circuits; The MCU digital control unit compares the target dimming duty cycle D received from the dimming signal input interface with a preset threshold: when D ≥ 50%, the first switching circuit is configured to handle the main output and the second switching circuit to handle the auxiliary output; when D < 50%, the second switching circuit is configured to handle the main output and the first switching circuit to handle the auxiliary output. Furthermore, the MCU digital control unit calculates the output power distribution ratios K1 and K2 of the first and second switching circuits in real time based on the detected current, voltage, and target dimming duty cycle D, with K1 + K2 = 1, and adjusts the operating parameters of the two switching circuits and the corresponding active power factor correction boost circuits accordingly, so that the switching circuit handling the main output always operates in its optimal efficiency range.

2. The LED street light digital intelligent dimming high-efficiency switching power supply according to claim 1, characterized in that, The switching conversion circuit adopts an LLC resonant converter topology and is controlled by an LLC resonant controller, which is one of the NCP13992, ICL5102, or MP4655 series chips. The active power factor correction boost circuit adopts a Boost topology and is controlled by a PFC controller, which is one of the BP2628, LM3447, TPS92075, or ICL5102 series chips. The main switching transistor of the switching conversion circuit is a silicon carbide MOSFET, and the switching conversion circuit also has a dedicated gate driver to drive the silicon carbide MOSFET. The gate drive voltage of the gate driver is +15V.

3. The LED street light digital intelligent dimming high-efficiency switching power supply according to claim 1, characterized in that, The synchronous rectification and filtering circuit includes a synchronous rectification controller and a synchronous rectification MOSFET driven by the synchronous rectification controller. The synchronous rectification controller detects the current direction of the output inductor of the switching circuit and controls the synchronous rectification MOSFET to conduct during the freewheeling current of the inductor.

4. The LED street light digital intelligent dimming high-efficiency switching power supply according to claim 1, characterized in that, The MCU digital control unit is a 32-bit microcontroller with a PWM output resolution of no less than 16 bits. The dimming signal input interface supports both PWM dimming signals and 0-10V analog dimming signals, and is equipped with an automatic identification circuit that automatically switches the working mode according to the type of input signal. When the junction temperature of the power device in any switching circuit exceeds a preset threshold, the MCU digital control unit automatically shifts the power distribution ratio of that circuit to the other circuit by a preset ratio to balance the heat load of the two circuits.

5. The LED street light digital intelligent dimming high-efficiency switching power supply according to claim 1, characterized in that, The output merging circuit uses MOSFET switches in conjunction with logic control circuits to achieve conflict-free merging of the two outputs. At any given time, only one output of the synchronous rectification and filtering circuit is allowed to be connected to the LED load, thus avoiding short circuit between the two outputs.

6. The LED street light digital intelligent dimming high-efficiency switching power supply according to claim 1, characterized in that, The power supply has an average conversion efficiency of no less than 97% and a peak efficiency of no less than 98.5% in the full dimming range of 0-100%; and a conversion efficiency of no less than 94% when the dimming duty cycle is less than 30%.

7. A control method for a high-efficiency switching power supply for digital intelligent dimming of LED streetlights as described in any one of claims 1 to 6, characterized in that, Includes the following steps: S1: The MCU digital control unit is powered on, initialized, and performs a self-test, reading the preset efficiency-power curve parameters; S2: The MCU digital control unit reads external dimming commands through the dimming signal input interface to obtain the target dimming duty cycle D, where 0%≤D≤100%; S3: The MCU digital control unit detects the output current Iout and output voltage Vout in real time through the current detection circuit and voltage detection circuit, and calculates the current output power Pout=Iout×Vout; S4: The MCU digital control unit determines the main and auxiliary circuits based on the comparison between the target dimming duty cycle D and the preset threshold: when D≥50%, the first switching circuit is the main circuit and the second switching circuit is the auxiliary circuit; when D<50%, the second switching circuit is the main circuit and the first switching circuit is the auxiliary circuit; and calculates the first output power allocation ratio K1 and the second output power allocation ratio K2 according to the preset efficiency optimization algorithm, K1+K2=1; S5: The MCU digital control unit calculates and outputs the control parameters of the two switching circuits according to K1 and K2 respectively, and dynamically adjusts the boost ratio of the two active power factor correction boost circuits. S6: The MCU digital control unit continuously monitors the output parameters and uses a PID closed-loop control algorithm to adjust the control quantity so that the output power follows the target dimming duty cycle D. When the junction temperature of the power device is detected to exceed the preset threshold, the power allocation ratio of that channel is automatically reduced. S7: Repeat steps S2 to S6 to achieve real-time dynamic optimization control.

8. The control method according to claim 7, characterized in that, The calculation method for the power allocation ratio in step S4 is as follows: When D≥50%, K1=0.5+0.8×(D-50%) / 50%, K2=1-K1; When D < 50%, K2 = 0.5 + 0.8 × (50% - D) / 50%, K1 = 1 - K2; The coefficient 0.8 ensures that the switching circuit, which bears the main output, maintains a load rate of no less than 15% even at the extreme dimming depth.

9. The control method according to claim 7, characterized in that, The control parameters mentioned in step S5 are the PWM duty cycle or switching frequency. The two switching circuits adjust their respective output power by changing the PWM duty cycle or switching frequency.

10. The control method according to claim 7, characterized in that, It also includes a remote monitoring step: the MCU digital control unit uploads operating parameters to the monitoring platform via UART or CAN interface, and supports online firmware upgrades.

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