LED dimming control circuit and control method thereof

Abstract

The invention discloses an LED dimming control circuit and a control method thereof.The LED dimming control circuit comprises a conversion module connected with a measured resistor, the conversion module comprises an operational amplifier circuit and a microcontroller, the operational amplifier circuit is configured to convert a resistance signal of the measured resistor into a corresponding voltage signal, and the microcontroller is configured to receive the voltage signal; the microcontroller is configured to calculate the sampled voltage signal to obtain a resistance value of the measured resistor, and convert the resistance value to obtain a corresponding PWM signal; the isolation device is used for transmitting the PWM signal output by the microcontroller to the dimming unit; the dimming unit is connected with the power output circuit; and the function extension module is connected with the microcontroller and is configured to acquire the actual voltage and the actual current of the power supply output circuit. A collaborative architecture with the microcontroller as a processing center and the basic analog circuit as a front end is established, so that the core of signal processing is completed in a digital domain, error accumulation of an analog signal chain is avoided, it is ensured that output current is highly matched with a set value, and auxiliary functions can be flexibly added without changing hardware.

Description

Technical Field

[0001] This invention relates to the field of dimming circuit technology, and in particular to an LED dimming control circuit and its control method. Background Technology

[0002] LEDset dimming solutions are widely used in the LED driver power supply field. The core of this solution lies in linearly adjusting the output current of the driver power supply by changing the resistance value of an external setting resistor (Rx), thereby achieving brightness adjustment of the LED light. In isolated constant current drive circuits, the signal reflecting the resistance value needs to be transmitted to the secondary side of the power supply to control the dimming chip. Currently, there are two main ways to implement LEDset functionality: the first is to build the circuit entirely using discrete analog components; this method results in a complex circuit structure, cumbersome debugging, and requires additional hardware circuitry for each new function (such as overpower protection or temperature protection), leading to increased system size, reduced reliability, and poor scalability. The second method uses dedicated integrated circuits (ASICs); although this method has relatively simpler external circuitry, dedicated chips typically integrate many complex functions, resulting in higher procurement costs and fixed functions, making flexible customization for specific applications difficult. Therefore, providing a solution with accurate transmission, good linearity, stable output, and low cost is a pressing issue.

[0003] The Chinese patent document "An LCC Circuit with LEDset2.0 Settable Current Circuit" (publication number CN109831846A, publication date 2019-05-31) includes: an AC-DC pre-stage filter and rectifier circuit, an LCC half-bridge resonant cavity circuit, an IC control circuit, a secondary rectifier and filter circuit, an LEDset circuit, and a load. The AC-DC pre-stage filter and rectifier circuit is electrically connected to the LCC half-bridge resonant cavity circuit; the LCC half-bridge resonant cavity circuit is electrically connected to the IC control circuit and the secondary rectifier and filter circuit; the IC control circuit is electrically connected to the LEDset circuit; and the secondary rectifier and filter circuit is connected to the load. This technology uses an integrated chip for LEDset dimming control. Although this method has a relatively simple peripheral circuit, dedicated chips are usually expensive to purchase and have fixed functions, making it difficult to customize them flexibly for specific applications. Summary of the Invention

[0004] The present invention aims to overcome the problems of existing LED set control schemes, which use all separate analog components, resulting in complex circuit structures, require additional hardware circuits to add new functions, leading to increased system size and reduced reliability, and the high cost of dedicated sampling integrated chips, which do not allow for flexible addition of functions. The present invention provides an LED dimming control circuit and its control method.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: An LED dimming control circuit includes: The conversion module connected to the resistor under test includes an operational amplifier circuit and a microcontroller. The operational amplifier circuit is configured to convert the resistance signal of the resistor under test into a corresponding voltage signal. The microcontroller is configured to calculate the resistance value of the measured resistor from the sampled voltage signal and convert it into a corresponding PWM signal. An isolation device transmits the PWM signal output by the microcontroller to the dimming unit; the dimming unit is connected to the power output circuit. The function expansion module connects to the microcontroller and is configured to acquire the actual voltage and current of the power output circuit.

[0006] This invention establishes a collaborative architecture with a microcontroller (MCU) as the intelligent processing center and basic analog circuits as the front end. In terms of hardware, an operational amplifier circuit linearly converts the resistance value of the measured resistor with a set current into a voltage signal, laying the foundation for high-precision processing. The microcontroller then performs digital filtering and precise calculations on the sampled signal, executes intelligent algorithms, and finally generates a PWM control signal for optocoupler isolation output. This architecture allows the core signal processing to be completed in the digital domain, avoiding the accumulation of errors in the analog signal chain and ensuring a high degree of consistency between the output current and the set value. Secondly, the programmable algorithm platform inside the microcontroller can easily integrate functions such as over-power protection, temperature protection, and current closed-loop compensation without modifying the hardware. Finally, using a lower-cost MCU instead of a dedicated integrated chip simplifies the peripheral circuitry, reduces material and production costs, and allows for flexible addition of auxiliary functions.

[0007] Preferably, the operational amplifier circuit is a non-inverting proportional amplifier circuit, including a first operational amplifier, a first resistor connected between the inverting input terminal and the output terminal of the first operational amplifier, and the resistor to be measured connected between the inverting input terminal and ground; a first reference voltage is connected to the non-inverting input terminal of the first operational amplifier; and the output terminal of the first operational amplifier outputs a voltage signal to the microcontroller.

[0008] Preferably, the voltage signal output from the output terminal of the first operational amplifier is divided by a voltage divider circuit composed of a second resistor and a third resistor, then filtered by a filter circuit composed of a fourth resistor and a first capacitor before being output to the microcontroller.

[0009] Preferably, the dimming control circuit further includes an auxiliary power supply unit, which draws power from the power output circuit and supplies power to the conversion module after rectification and linear regulation.

[0010] Preferably, in the functional expansion module, the output signal from the power output circuit is input to the microcontroller for actual voltage acquisition after passing through a voltage divider circuit and a filter circuit; the output signal is input to the microcontroller for actual current acquisition after passing through a second in-phase amplifier circuit and a filter circuit. The functional expansion module also includes a temperature acquisition circuit, which uses a thermistor to acquire the power supply temperature.

[0011] A control method for an LED dimming control circuit includes: The resistance signal of the resistor under test is converted into a voltage signal for sampling, and the resistance value of the resistor under test is calculated based on the sampled value. The target output current is calculated based on the resistance value of the measured resistor, and the duty cycle of the PWM signal is determined based on the target output current. The corresponding PWM signal is generated based on the duty cycle of the PWM signal and output to the dimming unit through an isolation device to control the output signal of the power output circuit.

[0012] Preferably, the step of calculating the target output current based on the resistance value of the measured resistor and determining the duty cycle of the PWM signal based on the target output current includes: The product of the resistance value of the resistor being measured and the target output current is a preset fixed value; The duty cycle of the PWM signal is the ratio of the target output current to the maximum current parameter.

[0013] Preferably, power limiting protection is also included after calculating the target output current; The target output power is calculated by multiplying the actual voltage and the target output current, and then subtracted from the rated power to calculate the single power deviation. The single power deviation is accumulated. When the accumulated result is greater than or equal to the preset power deviation threshold, power limiting protection is implemented, and the rated power divided by the actual voltage is used as the target output current.

[0014] Preferably, after determining the duty cycle of the PWM signal, the single current deviation between the target output current and the actual current is calculated. If the single current deviation is greater than or equal to the preset current deviation threshold, the duty cycle is compensated according to the set percentage step.

[0015] Preferably, after determining the duty cycle of the PWM signal, temperature-assisted correction is also included: The actual power supply temperature is compared with a preset temperature threshold. If the power supply temperature is greater than the temperature threshold, the duty cycle of the PWM signal is multiplied by a preset reduction factor to reduce the derating, and an updated duty cycle is generated to produce the PWM signal.

[0016] This invention offers the following advantages: High precision and high linearity: By utilizing a microcontroller's high-precision ADC for sampling and processing signals through digital calculations and software algorithms, distortion and nonlinearity issues inherent in pure analog signal transmission are avoided, achieving a high degree of fidelity and excellent linearity between the actual current and the measured resistance; Scalability and intelligence: Based on the microcontroller's control algorithm, functions can be flexibly added or modified without hardware modifications. It integrates intelligent functions such as over-power protection, current closed-loop compensation, and temperature protection, greatly improving the product's reliability, safety, and adaptability; Low cost and simple design: By using a single-chip microcontroller (MCU) as the microcontroller instead of a dedicated chip, combined with analog front-end circuitry, hardware material costs are reduced. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the LED dimming control circuit in this invention.

[0018] Figure 2 This is a circuit diagram of the boost power supply circuit in this invention.

[0019] Figure 3 This is a circuit diagram of the dimming unit in this invention.

[0020] Figure 4 This is a circuit diagram of the power output circuit in this invention.

[0021] Figure 5 This is a circuit diagram of the auxiliary power supply unit in this invention.

[0022] Figure 6 This is a circuit diagram of the conversion module and the function expansion module in this invention.

[0023] Figure 7 This is a flowchart of the control method of the LED dimming control circuit in this invention. Detailed Implementation

[0024] The present invention will now be further described with reference to the accompanying drawings and specific embodiments.

[0025] like Figure 1-6 As shown, an LED dimming control circuit includes: The conversion module connected to the resistor under test includes an operational amplifier circuit and a microcontroller. The operational amplifier circuit is configured to convert the resistance signal of the resistor under test into a corresponding voltage signal. The microcontroller is configured to calculate the resistance value of the measured resistor from the sampled voltage signal and convert it into a corresponding PWM signal; An isolation device transmits the PWM signal output by the microcontroller to the dimming unit; the dimming unit is connected to the power output circuit. The function expansion module connects to the microcontroller and is configured to acquire the actual voltage and current of the power output circuit.

[0026] This invention establishes a collaborative architecture with a microcontroller (MCU) as the intelligent processing center and basic analog circuits as the front end. In terms of hardware, an operational amplifier circuit linearly converts the resistance value of the measured resistor with a set current into a voltage signal, laying the foundation for high-precision processing. The microcontroller then performs digital filtering and precise calculations on the sampled signal, executes intelligent algorithms, and finally generates a PWM control signal for optocoupler isolation output. This architecture allows the core signal processing to be completed in the digital domain, avoiding the accumulation of errors in the analog signal chain and ensuring a high degree of consistency between the output current and the set value. Secondly, the programmable algorithm platform inside the microcontroller can easily integrate functions such as over-power protection, temperature protection, and current closed-loop compensation without modifying the hardware. Finally, using a lower-cost MCU instead of a dedicated integrated chip simplifies the peripheral circuitry, reduces material and production costs, and allows for flexible addition of auxiliary functions.

[0027] The dimming control circuit of this invention comprises eight parts: a boost power supply circuit, a dimming unit, a power output circuit, an isolation device, a conversion module, a measured resistor, an auxiliary power supply unit, and a functional expansion module. The isolation device can be an optocoupler, used as the connection between the conversion module and the dimming unit. The PWM signal output from the microcontroller of the conversion module is input to the transmitter of the optocoupler. The receiver of the optocoupler receives the signal from the transmitter and controls the dimming of the dimming unit, thereby controlling the output signal of the power output circuit to supply power to the LED.

[0028] The boost power supply circuit serves as the power input to the dimming unit. The dimming chip within the unit regulates and controls the dimming, ultimately outputting a power signal to the LED through the power output circuit for dimming. The M terminal of the boost power supply circuit is connected to the M terminal of the dimming unit, and the N terminal is connected to the N terminal of the dimming unit. A transformer connects the output of the dimming unit to the input of the power output circuit.

[0029] This invention improves the dimming control circuit and control method. Therefore, the focus is on improving the circuits of the conversion module, auxiliary power supply unit, function expansion module, and measured resistor. In the dimming unit, an optocoupler is set up to connect with the conversion module. The PWM signal received by the receiving end of the optocoupler is used as input to the dimming chip for dimming control. In the power output circuit, power is drawn from the winding of the transformer to supply power to the auxiliary power supply unit. At the same time, the output end of the power output circuit is connected to the function expansion module to collect the actual voltage and actual current.

[0030] As a specific example, such as Figure 6As shown, the conversion module mainly includes a microcontroller and an operational amplifier circuit that are interconnected. The operational amplifier circuit linearly converts the resistance signal of the resistor to be measured into a voltage signal, which is then sampled by the high-precision ADC of the microcontroller. The PWM output terminal of the microcontroller outputs a PWM signal and connects it to the dimming unit through an isolation optocoupler.

[0031] The operational amplifier circuit is designed as a non-inverting proportional amplifier circuit, including a first operational amplifier, a first resistor connected between the inverting input terminal and the output terminal of the first operational amplifier, and the resistor to be measured connected between the inverting input terminal and ground; a first reference voltage is connected to the non-inverting input terminal of the first operational amplifier; and the output terminal of the first operational amplifier outputs a voltage signal to the microcontroller.

[0032] Specifically, the resistor Rx to be measured is connected between terminals X2F and X2G. A Zener diode ZS104 is connected in parallel across the resistor Rx to protect against overvoltage surges. The anode of diode DS107 is connected to X2F, and the cathode of diode DS107 is connected to the positive terminal of the 12V power supply. X2F is connected to the inverting input of operational amplifier US51B, and the inverting input of US51B is connected to the output of US51B through resistor RS54D. A 5V regulated power supply is connected to resistor RS55 and capacitor CS55D for RC filtering before being input to the non-inverting input of operational amplifier US51B. The ingenuity of this circuit lies in its output voltage Uout = 5V*(1 + RS54D / Rx), which linearly amplifies the change in the measured resistor Rx into a precisely measurable voltage.

[0033] To ensure the signal fed into the microcontroller is stable and within its measurement range, the voltage signal output from the first operational amplifier is divided by a voltage divider circuit composed of a second and third resistor, and then filtered by an RC filter circuit composed of a fourth resistor and a first capacitor, ultimately generating a clean detection voltage output to the microcontroller. Based on the known circuit parameters (resistance and capacitance values ​​of the voltage divider and filter circuits), the microcontroller can accurately calculate the true resistance value of the measured resistor Rx through simple mathematical inversion. Compared to directly measuring resistance, this method has stronger anti-interference capabilities and higher accuracy.

[0034] Specifically, the output of operational amplifier US51B is connected to one end of resistor RS54B and one end of resistor RS54A via resistor RS54C. The other end of resistor RS54B is grounded, and the other end of resistor RS54A is grounded via capacitor CS55B and connected to the first ADC sampling terminal ADC1 of microcontroller US54. Microcontroller US54 can be a single-chip microcontroller of model HC89F0332. The PWM terminal of microcontroller US54 outputs a PWM signal and is connected to the transmitter of the isolation optocoupler via RS53.

[0035] Optionally, the functional expansion module includes the acquisition of actual voltage, actual current, and temperature, which can greatly enhance the system's sensing and protection capabilities.

[0036] The output signal from the power output circuit is input to the microcontroller for actual voltage acquisition after passing through a voltage divider and filter circuit. Specifically, the power signal from the LED+ terminal of the power output circuit is connected to one end of resistor RS52B and one end of resistor RS52C via resistor RS52A. The other end of resistor RS52B is grounded, and the other end of resistor RS52C is grounded through capacitor CS55A and connected to the third ADC sampling terminal ADC3 of the microcontroller US54.

[0037] The output signal, after passing through the second non-inverting amplifier circuit and the filter circuit, is input to the microcontroller for actual current acquisition. Specifically, the LED-terminal power signal from the power output circuit is connected via resistor RS56 to one end of capacitor CS55E and the non-inverting input of operational amplifier US51A, with the other end of capacitor CS55E grounded. The inverting input of operational amplifier US51A is grounded via resistor RS57 and connected to the output of operational amplifier US51A via resistor RS58. The output of operational amplifier US51A is grounded via capacitor CS55C and connected to the second ADC sampling terminal ADC2 of microcontroller US54.

[0038] The functional expansion module also includes a temperature acquisition circuit, which uses a thermistor to acquire the power supply temperature. Specifically, one end of the thermistor RS53B is grounded, and the other end is connected to resistor RS53A and the temperature detection input terminal PA4 of the microcontroller US54. The other end of resistor RS53A is connected to a +5V voltage.

[0039] As a specific embodiment, the dimming control circuit also includes an auxiliary power supply unit. This unit draws power from the power output circuit, and after rectification and linear regulation, supplies power to the conversion module. The design of the auxiliary power supply unit ensures the stable operation of the control circuit.

[0040] like Figure 4 , 5As shown, the input terminal A of the auxiliary power supply unit is connected to terminal A of the winding in the power output circuit, drawing power from the winding of its transformer. Diode DS52 is connected to the cathode of Zener diode ZS52 and one end of capacitor CS51. The anode of Zener diode ZS52 is connected to one end of resistor RS51B and the collector of transistor QS52. The other end of resistor RS51B is connected to the base of transistor QS52 and the cathode of Zener diode ZS51. The other end of capacitor CS51 and the anode of Zener diode ZS51 are both grounded. The emitter of transistor QS52 is connected to the +12V power supply, one end of capacitor CS52, the positive terminal of electrolytic capacitor C8, and the voltage input terminal of voltage regulator chip US52. Resistor RS51C is connected between the collector and emitter of transistor QS52. The other end of capacitor CS52 and the negative terminal of electrolytic capacitor C8 are both grounded. The voltage output terminal of the voltage regulator chip US52 is connected to the positive terminal of the electrolytic capacitor C10 and outputs a +5V voltage to power the conversion module. The negative terminal of the electrolytic capacitor C10 is grounded.

[0041] This invention, based on the conversion module in the LED dimming control circuit, also provides, for example... Figure 7 The control method of the LED dimming control circuit shown includes: The resistance signal of the resistor under test is converted into a voltage signal for sampling, and the resistance value of the resistor under test is calculated based on the sampled value. The target output current is calculated based on the resistance value of the measured resistor, and the duty cycle of the PWM signal is determined based on the target output current. The corresponding PWM signal is generated based on the duty cycle of the PWM signal and output to the dimming unit through an isolation device to control the output signal of the power output circuit.

[0042] It should be noted that the resistance value of the resistor being measured in this invention is obtained through numerical calculation in the microcontroller by combining the parameters of each component in the in-phase amplifier circuit. Based on... Figure 6The conversion module circuit diagram shown depicts a non-inverting amplifier circuit composed of resistor RS54D and the measured resistor Rx. RS54D is a known standard resistor, meaning the output voltage Uout of op-amp US51B is 5V * (1 + RS54D / Rx) (Formula 1). Uout is then divided by resistors RS54C and RS54B, resulting in Udim = Uout * RS54B / (RS54C + RS54B) (Formula 2). Assuming RS54C = RS54B, Udim = 1 / 2 * Uout. Udim is then filtered by resistor RS54A and capacitor CS55B before being fed to the first ADC sampling terminal of microcontroller US54. Based on the sampled voltage value, microcontroller US54 calculates the corresponding resistance value of the measured resistor Rx by reverse engineering using Formulas 1 and 2.

[0043] The ADC sampling terminal in the microcontroller can be preset with a fixed sampling interval, such as sampling the signal once every 200ms. The sampling range includes the voltage value corresponding to the measured resistor Rx (and thus calculate the corresponding resistance value), the actual voltage and current of the power supply output circuit, and the temperature of the power supply. After each sampling is completed, the resistance value is calculated, the target output current is calculated, the duty cycle is calculated, and the PWM signal is generated and output to the dimming unit for dimming control.

[0044] For the resistance value of the measured resistor Rx obtained from sampling, as well as the actual voltage and current of the power supply output circuit, a combination of moving average filtering and mutation verification is used. The size of the moving average window can be set according to the system response requirements (e.g., 4 or 8 times) to effectively suppress random noise. The mutation verification rule is set as follows: if the difference between the current sampled value and the previous filtering result exceeds 50% of the full scale (configurable), it is determined to be an interference signal, this data is discarded, and the effective filtering value from the previous time is used, thereby effectively combating external spike pulse interference.

[0045] The sampled temperature data also employs a moving average filter, using a larger window (e.g., 16 samples) to accommodate slowly changing signals. A lookup table-based temperature calibration method is specifically designed for NTC thermistors. The microcontroller internally stores an NTC resistance-temperature correspondence table. The filtered temperature ADC value is converted into a precise temperature value through a lookup table combined with linear interpolation, which offers higher accuracy than simply using formulas.

[0046] It's worth noting that once the performance parameters of the constant current drive circuit are defined, the rated power P_ref, minimum current parameter Iout_min, and maximum current parameter Iout_max are all known values. Therefore, they can be input and stored in the microcontroller for direct use during subsequent control processes. The power deviation threshold ΔP_step and current deviation threshold ΔI_step are also pre-set values, such as 1% of the rated value. The duty cycle compensation ΔD, used for duty cycle compensation, can also be pre-set to a fixed percentage, such as 0.1%.

[0047] After obtaining the resistance value of the measured resistor, the target output current is calculated based on that resistance value. The product of the measured resistor Rx and the target output current Iset is a preset fixed value; for example, Iset = 5 / Rx. This is a predefined method of adjusting the current using a resistor. Normal dedicated chips generally use a direct proportional adjustment method for current setting, while this application uses an inverse proportional adjustment method. Compared to dedicated chips, this application allows for adjustment with a larger resistor when a smaller current is needed, while eliminating the need for a resistor during full-current output, thus simplifying user operation.

[0048] After obtaining the target output current Iset, the duty cycle D is further determined. The duty cycle D of the PWM signal is the ratio of the target output current Iset to the maximum current parameter Iout_max, D = Iset / Iout_max. The maximum current parameter is defined as the current when the duty cycle is 100%, which is a known quantity given the circuit.

[0049] After determining the duty cycle of the PWM signal, the microcontroller generates a corresponding PWM signal based on the duty cycle and outputs it from the PWM terminal of the microcontroller US54. The PWM signal is then input to the dimming unit through an isolation optocoupler to control the dimming output of the LED power drive circuit.

[0050] As a specific implementation, power limiting protection is also included after calculating the target output current. By acquiring the actual voltage Vo and calculating the target output current Iset, the microcontroller can calculate the actual target output power Po in real time. When the power exceeds the rated value, the microcontroller will immediately intervene and dynamically reduce the target output current Iset to achieve over-power protection. This protection is adaptive and smooth, superior to simple hardware shutdown.

[0051] Specifically, the target output power Po is calculated by multiplying the actual voltage Vo and the target output current Iset, Vo*Iset, and then subtracting this product from the rated power P_ref to calculate the single-cycle power deviation ΔP, i.e., ΔP = Po - P_ref. If the single-cycle power deviation ΔP is greater than or equal to the preset power deviation threshold ΔP_step (which can be set to one percent of the rated power), output power protection is applied, and the target output current Iset = P_ref / Vo is recalculated. This single-cycle power deviation is defined based on a sampling interval of 200ms, meaning that data is sampled once every sampling interval, and a single-cycle power deviation is calculated.

[0052] If a single power deviation ΔP is less than the power deviation threshold ΔP_step, the single power deviation is accumulated. When the accumulated result is greater than or equal to the preset power deviation threshold ΔP_step, power limiting protection is implemented, and the target output current Iset is obtained by dividing the rated power P_ref by the actual voltage Vo. Simultaneously, the accumulated deviation is cleared to zero, and the accumulation calculation restarts. This mechanism of "accumulating small deviations and responding instantly to large deviations" prevents malfunctions caused by minor fluctuations and allows for rapid responses to continuous minor overpower or severe instantaneous overpower.

[0053] The duty cycle of the PWM signal to be generated in the microcontroller is determined by the target output current after power limiting protection.

[0054] Furthermore, to address the static deviation between the actual output current Io and the target value Iset, a closed-loop compensation mechanism is introduced. After determining the duty cycle D of the PWM signal, the single-cycle current deviation ΔI = Iset - Io between the target output current Iset and the actual current Io is calculated. If the single-cycle current deviation ΔI is greater than or equal to the preset current deviation threshold ΔI_step, duty cycle compensation D = D + ΔD is performed according to the set percentage step size ΔD.

[0055] The direction of ΔD depends on the sign of the deviation. When the target output current Iset is less than the actual current Io, the single-cycle current deviation ΔI is negative, requiring an increase in the duty cycle. When the target output current Iset is greater than the actual current Io, the single-cycle current deviation ΔI is positive, requiring a decrease in the duty cycle. The duty cycle compensation can be configured as a fixed step or proportional to the deviation. This mechanism automatically compensates for system errors caused by component aging, temperature drift, etc., ensuring extremely high stability of the output current during long-term operation.

[0056] As an optional embodiment, after determining the duty cycle of the PWM signal, a temperature-assisted correction is also included: The actual power supply temperature T is compared with the preset temperature threshold 0.9*Tmax. If the power supply temperature is greater than the temperature threshold, the duty cycle D of the PWM signal is multiplied by a preset reduction factor (e.g., 0.8) to reduce the PWM signal and obtain the updated duty cycle.

[0057] In this invention, the temperature threshold is the upper temperature limit multiplied by a preset scaling factor (e.g., 0.9, which can also be set according to actual conditions), thereby achieving predictive temperature derating protection. When the temperature T exceeds the temperature threshold, the microcontroller will forcibly multiply the currently calculated duty cycle D by a reduction factor (e.g., 0.8), i.e., D = D * 0.8, actively reducing the output power to reduce heat generation and prevent the device from being damaged by overheating or triggering a hard shutdown, thereby improving the system reliability and user experience.

[0058] After all calculations, verifications, and protection logic, the final safe PWM duty cycle D is obtained. The microcontroller writes this to the PWM timer's compare register and generates the corresponding PWM signal, which is output through an optocoupler. Simultaneously, the microcontroller records all key parameters of the current cycle (measured resistance Rx, actual voltage Vo, actual current Io, power supply temperature T, duty cycle D, etc.) and any abnormal flags for system status diagnosis and subsequent analysis.

[0059] The above embodiments are further elaborations and descriptions of the present invention to facilitate understanding, and are not intended to limit the present invention in any way. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An LED dimming control circuit, characterized in that, include: The conversion module connected to the resistor under test includes an operational amplifier circuit and a microcontroller. The operational amplifier circuit is configured to convert the resistance signal of the resistor under test into a corresponding voltage signal. The microcontroller is configured to calculate the resistance value of the measured resistor from the sampled voltage signal and convert it into a corresponding PWM signal. An isolation device transmits the PWM signal output by the microcontroller to the dimming unit; the dimming unit is connected to the power output circuit. The function expansion module connects to the microcontroller and is configured to acquire the actual voltage and current of the power output circuit.

2. The LED dimming control circuit according to claim 1, characterized in that, The operational amplifier circuit is a non-inverting proportional amplifier circuit, including a first operational amplifier, a first resistor connected between the inverting input terminal and the output terminal of the first operational amplifier, and the resistor to be measured connected between the inverting input terminal and ground; a first reference voltage is connected to the non-inverting input terminal of the first operational amplifier; and the output terminal of the first operational amplifier outputs a voltage signal to the microcontroller.

3. The LED dimming control circuit according to claim 2, characterized in that, The voltage signal output from the first operational amplifier is divided by a voltage divider circuit composed of a second resistor and a third resistor, then filtered by a filter circuit composed of a fourth resistor and a first capacitor, and finally output to the microcontroller.

4. An LED dimming control circuit according to claim 1, 2, or 3, characterized in that, The dimming control circuit also includes an auxiliary power supply unit, which draws power from the power output circuit and supplies power to the conversion module after rectification and linear regulation.

5. The LED dimming control circuit according to claim 4, characterized in that, In the aforementioned functional expansion module, the output signal from the power output circuit is input to the microcontroller after passing through a voltage divider circuit and a filter circuit to acquire the actual voltage; the output signal is input to the microcontroller after passing through a second in-phase amplifier circuit and a filter circuit to acquire the actual current. The functional expansion module also includes a temperature acquisition circuit, which uses a thermistor to acquire the power supply temperature.

6. A control method for an LED dimming control circuit, applicable to the LED dimming control circuit as described in any one of claims 1-5, characterized in that, include: The resistance signal of the resistor under test is converted into a voltage signal for sampling, and the resistance value of the resistor under test is calculated based on the sampled value. The target output current is calculated based on the resistance value of the measured resistor, and the duty cycle of the PWM signal is determined based on the target output current. The corresponding PWM signal is generated based on the duty cycle of the PWM signal and output to the dimming unit through an isolation device to control the output signal of the power output circuit.

7. The control method for an LED dimming control circuit according to claim 6, characterized in that, The calculation of the target output current based on the resistance value of the measured resistor, and the determination of the duty cycle of the PWM signal based on the target output current, include: The product of the resistance value of the resistor being measured and the target output current is a preset fixed value; The duty cycle of the PWM signal is the ratio of the target output current to the maximum current parameter.

8. A control method for an LED dimming control circuit according to claim 6 or 7, characterized in that, After calculating the target output current, power limiting protection is also included; The target output power is calculated by multiplying the actual voltage and the target output current, and then subtracted from the rated power to calculate the single power deviation. The single power deviation is accumulated. When the accumulated result is greater than or equal to the preset power deviation threshold, power limiting protection is implemented, and the rated power divided by the actual voltage is used as the target output current.

9. A control method for an LED dimming control circuit according to claim 6 or 7, characterized in that, After determining the duty cycle of the PWM signal, the single current deviation between the target output current and the actual current is calculated. If the single current deviation is greater than or equal to the preset current deviation threshold, the duty cycle is compensated according to the set percentage step.

10. The control method for an LED dimming control circuit according to claim 8, characterized in that, After determining the duty cycle of the PWM signal, temperature-assisted correction is also included: The actual power supply temperature is compared with a preset temperature threshold. If the power supply temperature is greater than the temperature threshold, the duty cycle of the PWM signal is multiplied by a preset reduction factor to reduce the derating, and an updated duty cycle is generated to produce the PWM signal.

Images