Adaptive load voltage LED dimming constant voltage power supply and overload protection method thereof

Abstract

The application provides an LED dimming constant voltage power supply with adaptive load voltage and an overload protection method thereof. The LED dimming constant voltage power supply comprises a main control circuit, a self-detection circuit, and an overload protection circuit. The main control circuit is used for outputting a first reference voltage signal to make a controlled voltage conversion circuit output a maximum voltage, outputting a PWM dimming signal to drive a first transistor through a chopper circuit, and outputting a switching signal to start voltage detection of a load. The self-detection circuit comprises a constant current source circuit and a first operation circuit. The constant current source circuit is connected with the load to form a constant current power supply loop. The first operation circuit is used for measuring a load voltage and outputting a voltage sampling signal to the main control circuit. The main control circuit outputs a second reference voltage signal to the controlled voltage conversion circuit according to the voltage sampling signal to make the controlled voltage conversion circuit adjust to output the load voltage. The application realizes load voltage detection and adjustment of load power supply voltage through the self-detection circuit, and realizes overload protection under different output voltages through the overload protection circuit.

Description

Technical Field

[0001] This invention relates to the field of dimming power supply technology, specifically to an adaptive load voltage LED dimming constant voltage power supply and its overload protection method. Background Technology

[0002] LED dimming power supplies are dedicated drive devices for LED lighting loads, converting input electrical energy into a stable power supply for the load and providing precise brightness adjustment. Currently, with the global lighting market's trend towards smarter and more energy-efficient designs, LED dimming power supplies and switching power supplies are widely used, and the market continues to expand. However, they still face the following challenges:

[0003] 1. Poor load voltage compatibility leads to high development and usage costs. Most existing LED dimming power supplies use a single voltage output, meaning they can only be matched to loads with a fixed operating voltage. Loads with different operating voltages require multiple dimming power supplies with different voltage outputs, which greatly increases the development costs for dimming power supply manufacturers and the number of SKUs (Stock Keeping Units) for users.

[0004] 2. Manual voltage switching is prone to errors. Some LED dimming power supplies support manual switching of the output voltage level, such as 24V-12V switching. Although this can reduce the number of SKUs for users, manual operation can easily lead to incorrect settings or incorrect load connections. If a high-voltage power supply is mistakenly connected to a low-voltage load, it can cause the load to burn out, resulting in additional losses and after-sales costs.

[0005] 3. Overload protection failure. The overload protection parameters of the LED dimming power supply cannot be adaptively adjusted under different output voltages, resulting in uneven overload protection. For example, an LED dimming power supply with 12V output will trigger protection when the overload is within 1.1 times, but when switching to 24V output, the overload needs to reach more than 1.3 times to trigger protection. In this case, the power supply will fail briefly due to overheating without protection, reducing the reliability of the LED dimming power supply.

[0006] Furthermore, if the transformer, inductor, and power devices of the power supply are designed and selected according to the maximum current and heat load at the highest voltage level in order to ensure that the LED dimming power supply does not overheat and be damaged at the highest voltage level, larger or more expensive components will be selected, which will result in waste of resources, increased production and manufacturing costs, and reduced market competitiveness.

[0007] Therefore, there is an urgent need to design an LED dimming constant voltage power supply and its overload protection method that can adapt to different load voltages and achieve effective overload protection under different output voltages. Summary of the Invention

[0008] This invention provides an adaptive load voltage LED dimming constant voltage power supply and its overload protection method, which solves the problems of poor compatibility with different load voltages, the need for manual switching of voltage output levels, and easy failure of overload protection in existing LED dimming power supplies. In this way, it can adapt to different load voltages and achieve overload protection under different output voltages.

[0009] The present invention achieves the above objectives through the following technical solutions:

[0010] An adaptive load voltage LED dimming constant voltage power supply includes a controlled voltage conversion circuit, a main control circuit, a chopper circuit, a first transistor, and a self-detection circuit. The controlled voltage conversion circuit receives a first power supply and converts it into a second power supply, which is output to the power input terminal of the chopper circuit and the positive terminal of the load. The negative terminal of the load is grounded through the first transistor. The first output terminal of the main control circuit is connected to the controlled terminal of the controlled voltage conversion circuit and outputs a first reference voltage signal to enable the controlled voltage conversion circuit to output its maximum voltage. Its second output terminal is connected to the PWM input terminal of the chopper circuit and outputs a PWM dimming signal to pass through the chopper circuit. The first transistor is driven; its third output terminal is connected to the input terminal of the self-detection circuit, and is used to output a switching signal to start the voltage detection of the load; the self-detection circuit includes a constant current source circuit and a first operational circuit, the constant current source circuit is connected to the load to form a constant current power supply loop; the input terminal of the first operational circuit is connected to both ends of the load, and is used to measure the load voltage and output a voltage sampling signal to the first input terminal of the main control circuit; the main control circuit outputs a second reference voltage signal to the controlled voltage conversion circuit according to the voltage sampling signal, and the controlled voltage conversion circuit is used to adjust the second power supply to the working voltage of the load according to the second reference voltage signal.

[0011] A further embodiment includes an EMI filter circuit and an AC-DC circuit. The EMI filter circuit is connected to an AC power supply and is used to filter and suppress noise before outputting the AC power supply to the AC-DC circuit. The AC-DC circuit includes a rectifier circuit and a multi-winding transformer. The rectifier circuit is used to rectify the AC power supply into DC power and output it to the primary winding of the multi-winding transformer. After voltage transformation, the multi-winding transformer outputs the first power supply, the third power supply, and the fourth power supply from multiple secondary windings. Its primary auxiliary winding is used to collect the first voltage feedback signal and output it to the main control circuit. The third power supply is used to power the main control circuit and the self-detection circuit.

[0012] A further embodiment includes a dimmer and a dimming circuit. The power supply terminal of the dimmer is input to the AC power supply for dimming operation and outputs a raw dimming signal to the dimming circuit. The power supply terminal of the dimming circuit is input to the fourth power supply for signal conversion and processing of the raw dimming signal and outputting a dimming signal to the second input terminal of the main control circuit. The main control circuit is used to output a PWM dimming signal with a corresponding duty cycle according to the magnitude of the dimming signal.

[0013] A further embodiment includes a controlled voltage conversion circuit comprising a voltage regulator circuit, a voltage output circuit, a sampling circuit, a control circuit, and a bias amplifier circuit. The voltage regulator circuit is used to regulate and convert the first power supply, and adjust the output voltage according to the first reference voltage signal or the second reference voltage signal, and output the second power supply through the voltage output circuit. The sampling circuit is connected to the output terminal of the voltage output circuit and is used to collect a second voltage feedback signal to the control circuit. The control circuit is used to output a bias control signal to the bias amplifier circuit according to the second voltage feedback signal. The bias amplifier circuit is used to amplify the bias control signal and output a bias voltage to the voltage regulator circuit. The voltage regulator circuit is used to adjust the input first power supply according to the bias voltage.

[0014] A further embodiment is that the voltage regulator circuit includes an error amplifier, a PWM comparator, and a power switch. The non-inverting input of the error amplifier receives the first reference voltage signal or the second reference voltage signal, its inverting input receives the bias voltage, and its output is connected to the inverting input of the PWM comparator. The non-inverting input of the PWM comparator receives the first reference voltage signal or the second reference voltage signal, and its output is connected to the control terminal of the power switch. The power switch outputs the second power supply.

[0015] A further embodiment is that the constant current source circuit includes a fourth transistor, a first operational amplifier, a second transistor, and a sixteenth resistor. The base of the fourth transistor is connected to the third output terminal of the main control circuit, its collector is connected to the third power supply and to the non-inverting input terminal of the first operational amplifier, and its emitter is grounded. The inverting input terminal of the first operational amplifier is grounded through the sixteenth resistor, its power supply terminal is connected to the third power supply, and its output terminal is connected to the base of the second transistor. The collector of the second transistor is connected to the negative terminal of the load.

[0016] A further embodiment is that the first operational circuit includes a second operational amplifier and a second to a sixth resistor. The non-inverting input terminal of the second operational amplifier is connected to the positive terminal of the load through a third resistor and grounded through the second resistor. Its inverting input terminal is connected to the collector of the second transistor through a fifth resistor and connected to its output terminal through the sixth resistor. Its output terminal is connected to the first input terminal of the main control circuit through a fourth resistor.

[0017] A further embodiment includes an overload protection circuit. The fourth output terminal of the main control circuit is connected to the input terminal of the overload protection circuit to output a reference current signal. The overload protection circuit includes a third operational amplifier, an eleventh resistor, an eighth resistor, a third transistor, and a fifth transistor. The non-inverting input terminal of the third operational amplifier is connected to the fourth output terminal of the main control circuit through the eleventh resistor; its inverting input terminal is connected to the source of the first transistor through the eighth resistor, and the source of the first transistor is grounded; its power supply terminal is connected to the third power supply, and its output terminal is connected to the base of the third transistor; the collector of the third transistor is connected to the third power supply and to the base of the fifth transistor, and its emitter is grounded; the collector of the fifth transistor is connected to the PWM input terminal of the chopper circuit, and its emitter is grounded.

[0018] An overload protection method for an adaptive load voltage LED dimming constant voltage power supply, applied to the aforementioned adaptive load voltage LED dimming constant voltage power supply, comprising:

[0019] The main control circuit outputs a first reference voltage signal with a 100% duty cycle, causing the controlled voltage conversion circuit to output its maximum voltage, and the output PWM dimming signal to be low. At this time, the first transistor is turned off. The constant current source circuit is started to provide constant current power to the load. At this time, the load voltage measured by the first operational circuit is automatically adjusted according to the change of the connected load, and a voltage sampling signal of the corresponding magnitude is output to the main control circuit. The main control circuit outputs a second reference voltage signal with a corresponding duty cycle according to the voltage sampling signal. The controlled voltage conversion circuit adjusts the second power supply to the magnitude of the load voltage according to the second reference voltage signal. The overload protection circuit collects the load current in real time and determines whether the load current exceeds the reference current value. If it does not exceed the reference current value, the PWM dimming signal is high. If it exceeds the reference current value, the PWM dimming signal is pulled low. At this time, the first transistor is turned off, the load current is zero, the PWM dimming signal returns to high level, and this process is repeated to enter the hiccup mode of the load.

[0020] A further solution is that the main control circuit includes a counter circuit, which has a protection threshold for calculating the number of times the load's power is restored during the hiccup mode. If the number of power restorations exceeds the protection threshold, it is determined to be a circuit fault. At this time, the PWM dimming signal is kept at a low level and the load is completely turned off.

[0021] Therefore, compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. This invention automatically identifies the load voltage through a self-detection circuit. The circuit structure is simple, requiring only an operational amplifier and simple peripheral circuitry to achieve load voltage self-detection. The main control circuit controls the controlled voltage conversion circuit to achieve output voltage regulation. Compared with traditional solutions, there is no need to manually switch voltage levels, which improves user convenience and stability. It can greatly reduce the user's SKU and the original factory's development costs, while also avoiding the risk of users manually switching voltage levels and burning out the load due to users accidentally selecting the wrong voltage level.

[0023] 2. After the output voltage of the dimming power supply is adjusted, the main control circuit provides a corresponding reference voltage protection threshold based on the output voltage, thereby realizing the constant power overload protection hiccup mode and adjusting the overload current threshold in real time. Compared with the traditional solution, this avoids the problem of uneven overload power.

[0024] 3. This invention periodically attempts to restart via a hiccup pattern during overload, automatically recovering from anomalies caused by recoverable faults such as brief overloads and sudden current surges, reducing unnecessary manual intervention. Simultaneously, the lights will flash, facilitating quick manual identification of overload faults. However, if the fault persists, setting a hiccup count limit will completely shut down the output, preventing power devices from enduring prolonged stress and causing irreversible damage such as overheating and burnout. This also reduces hiccup losses, improving safety and extending the power supply's lifespan.

[0025] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0026] Figure 1 This is a block diagram of an adaptive load voltage LED dimming constant voltage power supply according to an embodiment of the present invention.

[0027] Figure 2 This is a schematic diagram of the constant current source circuit of the adaptive load voltage LED dimming constant voltage power supply according to an embodiment of the present invention.

[0028] Figure 3 This is a schematic diagram of the first operational circuit of the adaptive load voltage LED dimming constant voltage power supply according to an embodiment of the present invention.

[0029] Figure 4This is a flowchart of an overload protection method for an adaptive load voltage LED dimming constant voltage power supply according to an embodiment of the present invention. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0031] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0032] An embodiment of an LED dimming constant voltage power supply with adaptive load voltage

[0033] See Figure 1 This invention relates to an adaptive load voltage LED dimming constant voltage power supply, comprising a controlled voltage conversion circuit 10, a main control circuit 20, a chopper circuit 30, a first transistor Q1, and a self-detection circuit 40. The controlled voltage conversion circuit 10 receives a first power supply V+ and converts it into a second power supply Vled+, which is output to the power input terminal of the chopper circuit 30 and the positive terminal of the load. The negative terminal of the load is grounded via the first transistor Q1. The first output terminal of the main control circuit 20 is connected to the controlled terminal of the controlled voltage conversion circuit 10 and outputs a first reference voltage signal to enable the controlled voltage conversion circuit 10 to output its maximum voltage. Its second output terminal is connected to the PWM input terminal of the chopper circuit 30 and outputs a PWM dimming signal to achieve the desired dimming effect. Wave circuit 30 drives first transistor Q1; its third output terminal is connected to the input terminal of self-detection circuit 40, and is used to output a switching signal SW to start the voltage detection of the load; self-detection circuit 40 includes a constant current source circuit and a first operational circuit, the constant current source circuit is connected to the load to form a constant current power supply loop; the input terminal of the first operational circuit is connected to both ends of the load, and is used to measure the load voltage and output a voltage sampling signal V_adc to the first input terminal of main control circuit 20; main control circuit 20 outputs a second reference voltage signal to controlled voltage conversion circuit 10 according to the voltage sampling signal V_adc, and controlled voltage conversion circuit 10 is used to adjust the second power supply Vled+ to the working voltage of the load according to the second reference voltage signal.

[0034] In this embodiment, an EMI filter circuit 50 and an AC-DC circuit 60 are also included. The EMI filter circuit 50 is connected to an AC power supply and is used to filter and suppress noise in the AC power supply before outputting it to the AC-DC circuit 60. The AC-DC circuit 60 includes a rectifier circuit and a multi-winding transformer. The rectifier circuit is used to rectify the AC power supply into DC power and output it to the primary winding of the multi-winding transformer. After voltage transformation, the multi-winding transformer outputs a first power supply V+, a third power supply VDD, and a fourth power supply VCC from multiple secondary windings. Its primary auxiliary winding is used to collect a first voltage feedback signal and output it to the main control circuit 20. The third power supply VDD is used to power the main control circuit 20 and the self-detection circuit 40.

[0035] Specifically, in this embodiment, the voltage ratio of the primary auxiliary winding to the secondary winding is equal to the ratio of the number of turns in both windings. Therefore, by monitoring the voltage of the primary auxiliary winding as the first voltage feedback signal, the actual values ​​of the output voltages of multiple secondary windings can be obtained indirectly and accurately through calculation. If the feedback voltage is directly collected from the secondary winding, noise and interference may be introduced by the power devices at the downstream end.

[0036] Specifically, in this embodiment, the main control circuit 20 compares the first voltage feedback signal with a set voltage value and generates an error signal, and adjusts the primary winding input voltage of the multi-winding transformer according to the error signal.

[0037] In this embodiment, a dimmer 70 and a dimming circuit 80 are also included. The power supply terminal of the dimmer 70 is input with the AC power supply for dimming operation and outputs a raw dimming signal to the dimming circuit 80. The power supply terminal of the dimming circuit 80 is input with a fourth power supply VCC for signal conversion and processing of the raw dimming signal and outputting a dimming signal to the second input terminal of the main control circuit 20. The main control circuit 20 is used to output the PWM dimming signal with a corresponding duty cycle according to the magnitude of the dimming signal.

[0038] Specifically, in this embodiment, the dimmer 70 may include a knob, a slider, a 0-10V controller, a DALI controller, etc., and its output signal format is diverse, such as variable resistance, 0-10V analog voltage, digital protocol signal, etc. The dimming circuit 80 converts these different signals into voltage signals that can be read by the main control circuit 20, such as ADC sampling signals.

[0039] In this embodiment, the controlled voltage conversion circuit 10 includes a voltage regulator circuit, a voltage output circuit, a sampling circuit, a control circuit, and a bias amplifier circuit. The voltage regulator circuit is used to regulate and convert the first power supply V+, and adjust the output voltage according to the first reference voltage signal or the second reference voltage signal, and output the second power supply Vled+ through the voltage output circuit. The sampling circuit is connected to the output terminal of the voltage output circuit and is used to collect the second voltage feedback signal to the control circuit. The control circuit is used to output a bias control signal to the bias amplifier circuit according to the second voltage feedback signal. The bias amplifier circuit is used to amplify the bias control signal and output a bias voltage to the voltage regulator circuit. The voltage regulator circuit is used to adjust the input first power supply V+ according to the bias voltage.

[0040] In this embodiment, the voltage regulator circuit includes an error amplifier, a PWM comparator, and a power switch. The non-inverting input of the error amplifier receives the first reference voltage signal or the second reference voltage signal, the inverting input receives the bias voltage, and its output is connected to the inverting input of the PWM comparator. The non-inverting input of the PWM comparator receives the first reference voltage signal or the second reference voltage signal, and its output is connected to the control terminal of the power switch. The power switch outputs a second power supply Vled+.

[0041] See Figure 2 In this embodiment, the constant current source circuit includes a fourth transistor Q4, a first operational amplifier U1A, a second transistor Q2, and a sixteenth resistor R16. The base of the fourth transistor Q4 is connected to the third output terminal of the main control circuit 20, its collector is connected to the third power supply VDD and is connected to the non-inverting input terminal of the first operational amplifier U1A, and its emitter is grounded. The inverting input terminal of the first operational amplifier U1A is grounded through the sixteenth resistor R16, its power supply terminal is connected to the third power supply VDD, and its output terminal is connected to the base of the second transistor Q2. The collector of the second transistor Q2 is connected to the negative terminal of the load.

[0042] Specifically, the constant current source circuit in this embodiment also includes resistors R13, R9, R12 and capacitor C4. The fourth transistor Q4 is connected to the switch signal SW through resistor R13 and to the third power supply VDD through resistor R9. The power supply terminal of the first operational amplifier U1A is also grounded through capacitor C4 for capacitor filtering of the input power supply, and its output terminal is connected to the base of the second transistor Q2 through resistor R12.

[0043] See Figure 2In this embodiment, the first operational circuit includes a second operational amplifier U1B and a second to a sixth resistor. The non-inverting input terminal of the second operational amplifier U1B is connected to the positive terminal of the load through a third resistor R3 and grounded through a second resistor R2. Its inverting input terminal is connected to the collector of the second transistor Q2 through a fifth resistor R5 and connected to its output terminal through a sixth resistor R6. Its output terminal is connected to the first input terminal of the main control circuit 20 through a fourth resistor R4.

[0044] See Figure 3 In this embodiment, an overload protection circuit 90 is also included. The fourth output terminal of the main control circuit 20 is connected to the input terminal of the overload protection circuit 90 to output a reference current signal I_adj. The overload protection circuit 90 includes a third operational amplifier U2A, an eleventh resistor R11, an eighth resistor R8, a third transistor Q3, and a fifth transistor Q5. The non-inverting input terminal of the third operational amplifier U2A is connected to the fourth output terminal of the main control circuit 20 through the eleventh resistor R11; its inverting input terminal is connected to the source of the first transistor Q1 through the eighth resistor R8, and the source of the first transistor Q1 is grounded; its power supply terminal is connected to the third power supply VDD, and its output terminal is connected to the base of the third transistor Q3; the collector of the third transistor Q3 is connected to the third power supply VDD and to the base of the fifth transistor Q5, and its emitter is grounded; the collector of the fifth transistor Q5 is connected to the PWM input terminal of the chopper circuit 30, and its emitter is grounded.

[0045] Specifically, the overload protection circuit 90 in this embodiment also includes resistors R15, R14, R10, and R7, and capacitors C3 and C2. The non-inverting input terminal of the third operational amplifier U2A is also grounded through resistor R15, and resistor R15 and the eleventh resistor R11 form a voltage divider circuit. Its inverting input terminal is also grounded through capacitor C3 for capacitor filtering of the current sampling signal, and its power supply terminal is also grounded through capacitor C2 for capacitor filtering of the input power supply. The base of the third transistor Q3 is connected to the third power supply VDD through resistor R10, and resistor R14 is connected in parallel between it and its emitter.

[0046] Specifically, in this embodiment, the first transistor Q1 is a MOS transistor, and the second to fifth transistors are bipolar transistors.

[0047] Specifically, the LED dimming constant voltage power supply in this embodiment has two working modes: dimming mode and adaptive voltage mode. When the LED1 lamp is connected or replaced, the working mode is switched from dimming mode to adaptive voltage mode.

[0048] The dimming modes include:

[0049] When dimming is performed, the dimmer 70 outputs a raw dimming signal to the dimming circuit 80. The dimming circuit 80 converts and processes the raw dimming signal and outputs a dimming signal to the main control circuit 20. The main control circuit 20 outputs a PWM dimming signal with a corresponding duty cycle to the chopper circuit 30 according to the magnitude of the dimming signal. The chopper circuit 30 outputs a corresponding drive signal to the gate of the first transistor Q1 according to the magnitude of the PWM dimming signal, and the first transistor Q1 is in the on state. At this time, the second power supply Vled+ flows sequentially through the positive terminal of the lamp LED1, the negative terminal of the lamp LED1, into the drain of the first transistor Q1, and the source of the first transistor Q1 through the resistor R1 to ground to form a first load circuit. The dimming function is achieved by adjusting the on and off states of the first transistor Q1 to control the current of the lamp LED1.

[0050] The adaptive voltage mode includes:

[0051] When LED1 is connected or replaced, the main control circuit 20 outputs a first reference voltage signal with a 100% duty cycle, causing the controlled voltage conversion circuit 10 to adjust to the maximum voltage output. That is, the second power supply is at this maximum voltage. At this time, the second power supply Vled+ > V_LED1, and V_LED1 is the operating voltage of LED1. The output PWM dimming signal is low, and the first transistor Q1 is in the off state. At this time, LED1 will not work through the first load circuit mentioned above.

[0052] When the main control circuit 20 outputs a low-level switch signal SW, the fourth transistor Q4 is off. The third power supply enters the non-inverting input of the first operational amplifier U1A through resistor R9. Due to the constant current source characteristic of the operational amplifier, according to the virtual open circuit principle, V_U1A+ = V_U1A- = VDD. Therefore, the voltage across the sixteenth resistor R16 is V_R16 = VDD, where V_U1A+ is the voltage at the non-inverting input of the first operational amplifier U1A, and V_U1A- is the voltage at the inverting input of the first operational amplifier U1A. According to the emitter follower principle of transistors, the base voltage of the second transistor Q2 is V_Q2B = V_Q2E + 0.7V, where V_Q2E is the emitter voltage of the second transistor Q2, V_Q2E = V_R16 = VDD, and 0.7V is the voltage drop. Therefore, the output voltage of the first operational amplifier U1A is V_OUT = VDD + 0.7V. At this point, the positive terminal of LED1 passes through the first operational circuit, the negative terminal passes through the second transistor Q2, resistor R1, and then to ground to form a second load circuit. The loop current of the second load circuit is I_led = VDD / R_16, and the loop current is changed by adjusting the resistance value of R_16.

[0053] When powered by a constant current source, the voltage across LED1 is V_LED1. Due to the differential operational amplifier proportional characteristics of the second operational amplifier U1B, the voltage value of the voltage sampling signal V_adc is V_LED1 * (R_6 / R_5), where R_6 and R_5 are the resistance values ​​of resistors R6 and R5, respectively. This formula is used to calculate the voltage sampling signal for different operating voltages connected to the lamp. The main control circuit 20 outputs a second reference voltage signal with a corresponding duty cycle based on the voltage sampling signal V_adc. The controlled voltage conversion circuit 10 adjusts the second power supply Vled+ to the operating voltage connected to the lamp based on the second reference voltage signal.

[0054] An embodiment of an overload protection method for an adaptive load voltage LED dimming constant voltage power supply

[0055] See Figure 4 This invention relates to an overload protection method for an adaptive load voltage LED dimming constant voltage power supply, applied to the aforementioned adaptive load voltage LED dimming constant voltage power supply, comprising:

[0056] S1: The main control circuit 20 outputs a first reference voltage signal with a 100% duty cycle, making the controlled voltage conversion circuit 10 output the maximum voltage and the output PWM dimming signal is at a low level. At this time, the first transistor Q1 is turned off.

[0057] S2: Start the constant current source circuit to provide constant current power to the load. At this time, the load voltage measured by the first operation circuit will be automatically adjusted according to the change of the connected load, and the voltage sampling signal V_adc of the corresponding size will be output to the main control circuit 20.

[0058] S3: The main control circuit 20 outputs a second reference voltage signal with a corresponding duty cycle according to the voltage sampling signal V_adc, and the controlled voltage conversion circuit 10 adjusts the second power supply Vled+ to the load voltage level according to the second reference voltage signal.

[0059] S4: The overload protection circuit 90 collects the load current in real time and determines whether the load current exceeds the reference current value. If it does not exceed the reference current value, the PWM dimming signal is at a high level. If it exceeds the reference current value, the PWM dimming signal is pulled low, the first transistor Q1 is turned off, the load current is zero, and the PWM dimming signal returns to a high level.

[0060] Repeat step S4; when overloaded, the load enters hiccup mode.

[0061] Specifically, this embodiment illustrates the adaptive voltage process of the LED dimming constant voltage power supply when the load voltage is the no-load voltage, a 12V lamp, a 24V lamp, a 36V lamp, and a 48V lamp:

[0062] When the load voltage is the no-load voltage, the second power supply outputs the maximum voltage. Since the lamp is not connected and Vled- is 0, the second operational amplifier U1B detects the maximum voltage input based on differential proportional calculation. After calculation, it outputs the voltage sampling signal V_adc to the main control circuit 20. At this time, the main control circuit 20 outputs the second voltage reference signal, which maintains a 100% duty cycle and outputs a PWM signal at a low level. The first transistor Q1 is in the off state, and the main control circuit 20 outputs the switch signal SW at a low level. Therefore, the voltage output of the dimming power supply is the maximum voltage output when the load is no-load.

[0063] When a 24V lamp is connected, the second power supply is at its maximum output voltage. At this time, LED1 will not operate through the first load circuit, but rather through the second load circuit powered by the constant current source circuit. The first arithmetic circuit detects the 24V input voltage of the lamp and calculates and outputs a voltage sampling signal V_adc to the main control circuit 20 through differential proportional calculation. The main control circuit 20 then outputs a second reference voltage signal with a corresponding duty cycle based on the voltage sampling signal V_adc. The controlled voltage conversion circuit 10 adjusts the second power supply Vled+ to a 24V output voltage based on the second reference voltage signal. At this time, the main control circuit 20 outputs a high-level PWM dimming signal, and the first transistor Q1 is turned on. LED1 will then operate through the first load circuit, and the dimming function is achieved by adjusting the on and off states of the first transistor Q1 to control the current of LED1. At the same time, the main control circuit 20 outputs a high-level switch signal SW. At this time, the fourth transistor Q4 is turned on, and the voltage at the non-inverting input terminal of the first operational amplifier U1A is low. Due to the virtual open circuit characteristic, the constant current source circuit does not work at this time. Therefore, when under load, the voltage output of the dimming power supply is the working voltage connected to the load.

[0064] The adaptive voltage process of the LED dimming constant voltage power supply when connected to 24V, 36V, and 48V lamps is similar to that of 24V lamps, and will not be described in detail here.

[0065] Specifically, the overload protection process in this embodiment includes:

[0066] The overload protection circuit 90 collects the source current of the first transistor Q1 in real time. This current is converted into a second voltage sampling signal through the eighth resistor R8 and output to the inverting input of the third operational amplifier U2A. The non-inverting input of the third operational amplifier U2A receives the reference current signal I_adj through the eleventh resistor R11. When the voltage at the inverting input of the third operational amplifier U2A is V_U2A-≤V_U2A+, the output of the third operational amplifier U2A is high, the third transistor Q3 is turned on, and the fifth transistor Q5 is turned off. At this time, the PWM dimming signal output is high, and the LED dimming constant voltage power supply is not overloaded and is in normal working condition.

[0067] When the voltage at the inverting input of the third operational amplifier U2A is V_U2A->V_U2A+, the output of the third operational amplifier U2A is low, the third transistor Q3 is off, and the third power supply is input to the base of the fifth transistor Q5 through resistor R7. The fifth transistor Q5 turns on, thus pulling the PWM dimming signal low. At this time, when the PWM dimming signal is low, the first transistor Q1 is off, V_U2A-≤V_U2A+, the output of the third operational amplifier U2A is high, the third transistor Q3 turns on again, and the fifth transistor Q5 turns off. The PWM dimming signal then returns to a high level, and this process repeats. Therefore, during the overload protection period, the PWM dimming signal is output alternately high and low, and the LED1 lamp enters a hiccup mode.

[0068] Specifically, in this embodiment, the main control circuit 20 sets a reference current signal I_adj according to the voltage value of the second power supply. I_adj = total load power / voltage value of the second power supply, which is usually 1.2 to 1.5 times the rated current of the load.

[0069] In this embodiment, the main control circuit includes a counter circuit. The counter circuit has a protection threshold for calculating the number of times the load's power is restored during the hiccup mode. If the number of power restorations exceeds the protection threshold, it is determined to be a circuit fault. At this time, the PWM dimming signal is kept at a low level and the load is completely turned off.

[0070] Specifically, the hiccup mode in this embodiment automatically recovers from anomalies caused by recoverable faults such as brief overloads and sudden current surges by periodically attempting restarts, reducing unnecessary manual intervention. Simultaneously, the lights will flash, facilitating quick manual identification of overload faults. However, if the fault persists, setting a hiccup count limit and then completely shutting off the output prevents power devices from being subjected to prolonged stress, which could lead to irreversible damage such as overheating and burnout, while also reducing the energy loss from hiccups.

[0071] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0072] The above embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention shall fall within the scope of protection claimed by the present invention.

Claims

1. A constant voltage power supply for LED dimming that adapts to load voltage, characterized in that, include: The system includes a controlled voltage conversion circuit, a main control circuit, a chopper circuit, a first transistor, and a self-detection circuit. The controlled voltage conversion circuit receives a first power supply and converts it into a second power supply, which is then output to the power input terminal of the chopper circuit and the positive terminal of the load. The negative terminal of the load is grounded via the first transistor. The first output terminal of the main control circuit is connected to the controlled terminal of the controlled voltage conversion circuit and outputs a first reference voltage signal to enable the controlled voltage conversion circuit to output its maximum voltage. Its second output terminal is connected to the PWM input terminal of the chopper circuit, and is used to output a PWM dimming signal to drive the first transistor through the chopper circuit; Its third output terminal is connected to the input terminal of the self-detection circuit and is used to output a switching signal to start the voltage detection of the load; the self-detection circuit includes a constant current source circuit and a first operational circuit. The constant current source circuit is connected to the load to form a constant current power supply loop; the input terminal of the first operational circuit is connected to both ends of the load and is used to measure the load voltage and output a voltage sampling signal to the first input terminal of the main control circuit; the main control circuit outputs a second reference voltage signal to the controlled voltage conversion circuit according to the voltage sampling signal. The controlled voltage conversion circuit is used to adjust the second power supply to the working voltage of the load according to the second reference voltage signal.

2. The LED dimming constant voltage power supply with adaptive load voltage according to claim 1, characterized in that: It also includes an EMI filter circuit and an AC-DC circuit. The EMI filter circuit is connected to an AC power supply and is used to filter and suppress noise before outputting the AC power supply to the AC-DC circuit. The AC-DC circuit includes a rectifier circuit and a multi-winding transformer. The rectifier circuit is used to rectify the AC power supply into DC power and output it to the primary winding of the multi-winding transformer. After voltage transformation, the multi-winding transformer outputs the first power supply, the third power supply, and the fourth power supply from multiple secondary windings, respectively. Its primary auxiliary winding is used to collect the first voltage feedback signal and output it to the main control circuit. The third power supply is used to power the main control circuit and the self-detection circuit.

3. The LED dimming constant voltage power supply with adaptive load voltage according to claim 2, characterized in that: It also includes a dimmer and a dimming circuit. The power supply terminal of the dimmer is input to the AC power supply for dimming operation and outputs a raw dimming signal to the dimming circuit. The power supply terminal of the dimming circuit is input to the fourth power supply for signal conversion and processing of the raw dimming signal and outputting a dimming signal to the second input terminal of the main control circuit. The main control circuit is used to output the PWM dimming signal with a corresponding duty cycle according to the magnitude of the dimming signal.

4. The LED dimming constant voltage power supply with adaptive load voltage according to claim 2, characterized in that: The controlled voltage conversion circuit includes a voltage regulator circuit, a voltage output circuit, a sampling circuit, a control circuit, and a bias amplifier circuit. The voltage regulator circuit is used to regulate and convert the first power supply, and adjust the output voltage according to the first reference voltage signal or the second reference voltage signal, and output the second power supply through the voltage output circuit. The sampling circuit is connected to the output terminal of the voltage output circuit and is used to collect the second voltage feedback signal to the control circuit. The control circuit is used to output a bias control signal to the bias amplifier circuit according to the second voltage feedback signal. The bias amplifier circuit is used to amplify the bias control signal and output a bias voltage to the voltage regulator circuit. The voltage regulator circuit is used to adjust the input first power supply according to the bias voltage.

5. The LED dimming constant voltage power supply with adaptive load voltage according to claim 4, characterized in that: The voltage regulator circuit includes an error amplifier, a PWM comparator, and a power switch. The non-inverting input of the error amplifier receives the first reference voltage signal or the second reference voltage signal, the inverting input receives the bias voltage, and the output is connected to the inverting input of the PWM comparator. The non-inverting input of the PWM comparator receives the first reference voltage signal or the second reference voltage signal, and the output is connected to the control terminal of the power switch. The power switch outputs the second power supply.

6. The LED dimming constant voltage power supply with adaptive load voltage according to claim 5, characterized in that: The constant current source circuit includes a fourth transistor, a first operational amplifier, a second transistor, and a sixteenth resistor. The base of the fourth transistor is connected to the third output terminal of the main control circuit, its collector is connected to the third power supply and to the non-inverting input terminal of the first operational amplifier, and its emitter is grounded. The inverting input terminal of the first operational amplifier is grounded through the sixteenth resistor, its power supply terminal is connected to the third power supply, and its output terminal is connected to the base of the second transistor. The collector of the second transistor is connected to the negative terminal of the load.

7. The LED dimming constant voltage power supply with adaptive load voltage according to claim 6, characterized in that: The first operational circuit includes a second operational amplifier and a second to a sixth resistor. The non-inverting input terminal of the second operational amplifier is connected to the positive terminal of the load through a third resistor and grounded through the second resistor. Its inverting input terminal is connected to the collector of the second transistor through the fifth resistor, and to its output terminal through the sixth resistor; Its output terminal is connected to the first input terminal of the main control circuit through a fourth resistor.

8. The LED dimming constant voltage power supply with adaptive load voltage according to claim 2, characterized in that: It also includes an overload protection circuit, wherein the fourth output terminal of the main control circuit is connected to the input terminal of the overload protection circuit for outputting a reference current signal; The overload protection circuit includes a third operational amplifier, an eleventh resistor, an eighth resistor, a third transistor, and a fifth transistor. The non-inverting input terminal of the third operational amplifier is connected to the fourth output terminal of the main control circuit through the eleventh resistor. Its inverting input terminal is connected to the source of the first transistor through the eighth resistor, and the source of the first transistor is grounded; Its power supply terminal is connected to the third power supply, and its output terminal is connected to the base of the third transistor; the collector of the third transistor is connected to the third power supply and to the base of the fifth transistor, and its emitter is grounded; the collector of the fifth transistor is connected to the PWM input terminal of the chopper circuit, and its emitter is grounded.

9. An overload protection method for an adaptive load voltage LED dimming constant voltage power supply, characterized in that, The LED dimming constant voltage power supply applied to the adaptive load voltage according to any one of claims 1-8 comprises: The main control circuit outputs a first reference voltage signal with a 100% duty cycle, causing the controlled voltage conversion circuit to output its maximum voltage, and the output PWM dimming signal to be low. At this time, the first transistor is turned off. The constant current source circuit is started to provide constant current power to the load. At this time, the load voltage measured by the first operational circuit is automatically adjusted according to the change of the connected load, and a voltage sampling signal of the corresponding magnitude is output to the main control circuit. The main control circuit outputs a second reference voltage signal with a corresponding duty cycle according to the voltage sampling signal. The controlled voltage conversion circuit adjusts the second power supply to the magnitude of the load voltage according to the second reference voltage signal. The overload protection circuit collects the load current in real time and determines whether the load current exceeds the reference current value. If it does not exceed the reference current value, the PWM dimming signal is high. If it exceeds the reference current value, the PWM dimming signal is pulled low. At this time, the first transistor is turned off, the load current is zero, the PWM dimming signal returns to high, and this process is repeated to enter the hiccup mode.

10. The overload protection method for the adaptive load voltage LED dimming constant voltage power supply according to claim 9, characterized in that: The main control circuit includes a counter circuit with a protection threshold for calculating the number of times the load's power is restored during the hiccup mode. If the number of power restorations exceeds the protection threshold, it is determined to be a circuit fault. At this time, the PWM dimming signal is kept at a low level and the load is completely turned off.

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