LED constant voltage control circuit and LED device

Abstract

The application relates to an LED constant voltage control circuit and an LED device, which comprise a control unit, a voltage detection module, a current detection module, a voltage output module, a voltage switching module and an LED load; the voltage detection module and the current detection module are connected with the control unit; the voltage output module is connected with the control unit, the output end of the voltage switching module and the LED load; wherein the voltage output module is used for outputting voltage to the LED load and controlling the turn-on or turn-off of the output voltage according to the PWM signal output by the control unit; the voltage switching module is connected with the control unit, the input end of the voltage switching module is connected with at least two power supply windings capable of providing different rated voltages, and the voltage switching module switches the output voltage according to the voltage switching signal output by the control unit. The circuit of the application can detect short circuit of the circuit before providing the load voltage, and can output different rated voltages to automatically match the LED load.

Description

Technical Field

[0001] This invention relates to the technical field of LED control, and in particular to an LED constant voltage control circuit and an LED device. Background Technology

[0002] LEDs (light-emitting diodes) are widely used in various lighting scenarios due to their advantages such as high efficiency, energy saving, and long lifespan. The LED constant voltage control device is the core component driving LED lights, providing power to the LED load by outputting a constant DC voltage (such as DC12V, DC24V, or DC36V).

[0003] Currently, common LED constant voltage control devices typically have a fixed output voltage. However, in practical applications, it is often necessary to use LED loads with different rated operating voltages simultaneously. For example, a lighting project may contain both 12V-driven LED strips and 24V-driven LEDs. Construction workers must configure separate control devices with corresponding output voltages for each LED load, which causes significant inconvenience and can easily lead to device mismatch with the load, causing the LEDs to malfunction or even be damaged.

[0004] Furthermore, existing LED constant voltage control devices have blind spots in short-circuit protection. In actual installations, there is usually a long distance of wire between the device and the LED load. When a short circuit occurs in the output line located at a remote position, or when the LED itself experiences an abnormal short circuit, the wire between the short circuit point and the control device becomes equivalent to a resistive load. At this time, traditional control devices often cannot effectively distinguish between this short-circuit state and the normal operating state of a resistive load, and will continuously output a large current, causing the wire to heat up rapidly, posing a significant safety hazard of fire. Summary of the Invention

[0005] Based on this, the purpose of the present invention is to provide an LED constant voltage control circuit and an LED device that can perform short circuit detection on the circuit before providing load voltage, and can automatically match different rated voltages to the LED load.

[0006] In a first aspect, this application provides an LED constant voltage control circuit, including a control unit, a voltage detection module, a current detection module, a voltage output module, a voltage switching module, and an LED load;

[0007] The voltage detection module and the current detection module are respectively connected to the control unit; wherein, the voltage detection module is used to detect the output voltage, and the current detection module is used to detect the output current, and respectively feeds back the detection signals to the control unit; The voltage output module is connected to the control unit, the output terminal of the voltage switching module, and the LED load, respectively; wherein, the voltage output module is used to output voltage to the LED load, and control the output voltage to be turned on or off according to the PWM signal output by the control unit; The voltage switching module is connected to the control unit. The input terminal of the voltage switching module is connected to at least two power windings that can provide different rated voltages, and the output voltage is switched according to the voltage switching signal output by the control unit.

[0008] In some possible implementations, the voltage switching module includes a relay, a drive circuit, a first power winding, and a second power winding. The coil of the relay is connected to the control unit through the drive circuit. The normally closed contact and normally open contact of the relay are respectively connected to the first power winding and the second power winding. The first power winding is used to output a first rated voltage, and the second power winding is used to output a second rated voltage. The first rated voltage is different from the second rated voltage.

[0009] In some possible implementations, the driving circuit includes a first transistor, a first driving current-limiting resistor, a second current-limiting resistor, and a first pull-down resistor; the first input terminal of the first transistor is connected to the voltage switching signal output pin of the control unit through the first driving current-limiting resistor, the first connection terminal of the first transistor is connected to one end of the coil of the relay through the second current-limiting resistor, the second connection terminal of the first transistor is grounded, and the two ends of the first pull-down resistor are respectively connected to the first input terminal and the second connection terminal of the first transistor. The voltage switching signal output by the control unit controls the first transistor to turn on or off, thereby controlling the relay to switch the output voltage between the first rated voltage and the second rated voltage.

[0010] In some possible implementations, the driving circuit further includes a freewheeling diode, a second transistor, a first capacitor, and a first Zener diode; the anode of the freewheeling diode is connected to the first terminal of the first transistor, the cathode of the freewheeling diode is connected to a DC power supply, the first input terminal of the second transistor is connected to the cathode of the first Zener diode, the anode of the first Zener diode is grounded, and the second terminal of the second transistor is grounded through the first capacitor.

[0011] In some possible implementations, the voltage output module includes a first driver chip, a third transistor, a fourth transistor, a third current-limiting resistor, a fourth current-limiting drive resistor, a second capacitor, and a second Zener diode. The PWM signal output pin of the control unit is connected to the input pin of the first driver chip through the third current-limiting resistor, and the output pin of the first driver chip is connected to the first input terminal of the third transistor through the fourth current-limiting drive resistor. The second connection terminal of the fourth transistor is connected to the power supply pin of the first driver chip, and the second connection terminal of the fourth transistor is also grounded through the second capacitor. The cathode of the second Zener diode is connected to the first input terminal of the fourth transistor, and the anode of the second Zener diode is grounded. The first connection terminal of the third transistor is connected to the output terminal of the voltage switching module. The second connection terminal of the third transistor is connected to both the voltage output module and the LED load. The first driver chip receives the PWM signal output by the control unit and controls the third transistor to turn on or off according to the PWM signal, thereby controlling the output voltage to be turned on or off.

[0012] In some possible implementations, the voltage output module further includes an optocoupler isolation unit, the input terminal of which is connected to the first pin of the control unit, and the output terminal of which is connected to the voltage switching module. The optocoupler isolation unit is used to receive the isolation signal output by the control unit and perform electrical isolation.

[0013] In some possible implementations, the voltage detection module includes a voltage comparison circuit, the voltage comparison circuit includes a detection diode, and the voltage comparison pin of the control unit is connected to the second connection terminal of the third transistor through the detection diode; The control unit controls the voltage output module to output a test voltage. The voltage comparison circuit samples the sampled voltage value output by the third transistor. When the sampled voltage value is lower than a preset voltage threshold, it is determined that there is no short circuit at the output terminal; otherwise, it is determined that there is a short circuit at the output terminal.

[0014] In some possible implementations, the current detection module includes a sampling resistor, an operational amplifier, a first resistor, a second resistor, a third resistor, a fifth current-limiting resistor, a third capacitor, and a fourth capacitor; The sampling resistor is disposed between the voltage output module and the voltage switching module. The non-inverting input terminal of the operational amplifier is connected to the output terminal of the sampling resistor through the first resistor. The non-inverting input terminal of the operational amplifier is also grounded through the third capacitor. The inverting input terminal of the operational amplifier is connected to the output terminal of the operational amplifier through the second resistor. The fourth capacitor is connected in parallel between the inverting input terminal and the output terminal of the operational amplifier. The inverting input terminal of the operational amplifier is also grounded through the third resistor. The output terminal of the operational amplifier is connected to the current detection pin of the control unit through the fifth current limiting resistor. The output current passes through the sampling resistor and is converted into a voltage signal, which is then input to the operational amplifier. After being amplified by the operational amplifier, the signal is input to the control unit.

[0015] In some possible implementations, the voltage detection module includes a first voltage divider resistor, a second voltage divider resistor, and a fifth capacitor; the voltage detection pin of the control unit is connected to the output terminal of the voltage output module through the first voltage divider resistor, and the voltage detection pin of the control unit is also grounded through the second voltage divider resistor and the fifth capacitor respectively.

[0016] Secondly, this application provides an LED device, which includes an LED constant voltage control circuit as described in any of the above claims.

[0017] This application provides an LED constant voltage control circuit and LED device, including a control unit, a voltage detection module, a current detection module, a voltage output module, and a voltage switching module. When the device starts, the control unit controls the voltage output module to output a test voltage lower than the LED's turn-on voltage. A voltage comparison circuit determines whether a short circuit has occurred at the output terminal. If a short circuit is detected, the control unit controls the voltage switching module to first output a lower first rated voltage. Based on the current detection value, it determines whether the LED load is lit, thus determining that the LED load's operating voltage is the first rated voltage. If the LED is not lit, the control unit switches to a higher second rated voltage to further match the LED load, thereby achieving automatic identification of the LED load's rated voltage. Compared to existing technologies, this application achieves "seamless" automatic identification of the LED load's rated voltage by first outputting a safe low voltage for short-circuit pre-detection, and then outputting different rated voltages in a stepped manner and detecting the load current for intelligent matching. This completely solves the problem of equipment mismatch caused by manual configuration errors. Meanwhile, by monitoring changes in electrical parameters throughout the entire process, from initial startup to stable operation, short-circuit faults in remote lines or loads can be identified promptly and accurately, and immediate shutdown protection measures can be taken, fundamentally eliminating the risk of wire overheating and fire caused by short-circuit current. This application achieves a dual breakthrough in convenience and safety for LED constant voltage control devices, significantly improving the product's intelligence and reliability. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the structure of an LED constant voltage control circuit provided in an embodiment of this application; Figure 2 This is a circuit diagram of an LED constant voltage control circuit provided in an embodiment of this application. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the protection scope of this application.

[0021] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to limit the embodiments of this application. The singular forms “a,” “the,” and “the” used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any or all possible combinations of one or more of the associated listed items.

[0022] In the following description, when referring to the accompanying drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims. In the description of this application, it should be understood that the terms "first," "second," "third," etc., are used only to distinguish similar objects and are not necessarily used to describe a specific order or sequence, nor should they be construed as indicating or implying relative importance. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0023] Furthermore, in the description of this application, unless otherwise stated, "multiple" means two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, or B alone. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0024] Please see Figures 1 to 2 This application provides an LED constant voltage control circuit, including a control unit U1, a voltage detection module 2, a current detection module 3, a voltage output module 4, a voltage switching module 5, and an LED load 6; The voltage detection module 2 and the current detection module 3 are respectively connected to the control unit U1; wherein, the voltage detection module 2 is used to detect the output voltage, and the current detection module 3 is used to detect the output current, and respectively feeds back the detection signals to the control unit U1; The voltage output module 4 is connected to the output terminals of the control unit U1, the voltage switching module 5, and the LED load 6, respectively; wherein, the voltage output module 4 is used to output voltage to the LED load 6, and control the output voltage to be turned on or off according to the PWM signal output by the control unit U1; The voltage switching module 5 is connected to the control unit U1. The input terminal of the voltage switching module 5 is connected to at least two power windings that can provide different rated voltages, and the output voltage is switched according to the voltage switching signal output by the control unit U1.

[0025] This application provides an LED constant voltage control circuit and LED device, including a control unit U1, a voltage detection module 2, a current detection module 3, a voltage output module 4, and a voltage switching module 5. When the device starts, the control unit U1 controls the voltage output module 4 to output a test voltage lower than the LED turn-on voltage. A voltage comparison circuit determines whether a short circuit has occurred at the output terminal. If a short circuit is found, the control unit U1 controls the voltage output to be turned off. If no short circuit is found, the control unit U1 controls the voltage switching module 5 to first output a lower first rated voltage and determines whether the LED load 6 is lit based on the current detection value, thus determining that the operating voltage of the LED load 6 is the first rated voltage. If it is not lit, the control unit U1 controls the voltage switching module 5 to switch to a higher second rated voltage to further match the LED load 6, thereby achieving automatic identification of the rated voltage of the LED load 6. After the LED load 6 stably outputs a load voltage, the control unit U1 performs output circuit detection and comparison. When the detected current value repeatedly exceeds the set amplitude of the initial stable value, it determines that an output short circuit exists, and the LED constant voltage control is restarted, and the initial short circuit detection is performed again. Compared to existing technologies, this application achieves seamless automatic identification of the rated voltage of the LED load by first outputting a safe low voltage for short-circuit pre-detection, and then intelligently matching different rated voltages while detecting the load current. This completely solves the equipment mismatch problem caused by manual configuration errors. Simultaneously, by monitoring changes in electrical parameters throughout the entire process from initial startup to stable operation, it can promptly and accurately identify short-circuit faults in remote lines or loads and immediately take shutdown protection measures, fundamentally eliminating the risk of wire overheating and fire caused by short-circuit current. This application represents a dual breakthrough in the convenience and safety of LED constant voltage control devices, significantly improving the product's intelligence and reliability.

[0026] In one embodiment, the voltage switching module 5 includes a relay RE1, a drive circuit, a first power supply winding, and a second power supply winding. The coil of the relay RE1 is connected to the control unit U1 through the drive circuit. The normally closed contact and normally open contact of the relay RE1 are respectively connected to the first power supply winding and the second power supply winding. The first power supply winding is used to output a first rated voltage, and the second power supply winding is used to output a second rated voltage. The first rated voltage is different from the second rated voltage.

[0027] The voltage switching module 5 is used to switch the output voltage value to match LED loads 6 with different rated voltages. In one embodiment, the relay RE1 is connected to power windings providing different rated voltages, such as the first power winding and the second power winding, and the voltage provided by the power windings can meet the needs of different LED loads 6. For example, the first rated voltage output by the first power winding can be 12V, and the second rated voltage output by the second power winding can be 24V. In other embodiments, the first and second rated voltage values ​​can be adjusted according to actual needs, such as 24V / 36V, etc.

[0028] The relay RE1 is an electrically controlled switch that controls the switching of contacts by energizing and de-energizing the coil. For example, when the coil of the relay RE1 is not energized, the normally closed contact is closed, outputting a first rated voltage; when the coil of the relay RE1 is energized, the normally open contact is closed, outputting a second rated voltage. The drive circuit is used to amplify the control signal to drive the relay RE1 to operate.

[0029] In one embodiment, the driving circuit includes a first transistor Q10, a first driving current-limiting resistor R11, a second current-limiting resistor R77, and a first pull-down resistor; the first input terminal of the first transistor Q10 is connected to the voltage switching signal output pin P2.7 of the control unit U1 through the first driving current-limiting resistor R11, the first connection terminal of the first transistor Q10 is connected to one end of the coil of the relay RE1 through the second current-limiting resistor R77, the second connection terminal of the first transistor Q10 is grounded, and the two ends of the first pull-down resistor R26 are respectively connected to the first input terminal and the second connection terminal of the first transistor Q10; The voltage switching signal output by the control unit U1 controls the first transistor Q10 to turn on or off, thereby controlling the relay RE1 to switch the output voltage between the first rated voltage and the second rated voltage.

[0030] Wherein, the first transistor Q10 is a current-controlled semiconductor switching device. In one embodiment, the first transistor Q10 is a triode, and the first input terminal, the first connection terminal, and the second connection terminal of the first transistor Q10 are the base, the collector, and the emitter, respectively.

[0031] The first transistor Q10 is connected to one end of the relay RE1 coil via the second current-limiting resistor R77, and the other end of the relay RE1 coil is connected to a DC power supply (e.g., +12V). The two ends of the first pull-down resistor R26 are respectively connected to the first input terminal and the second connection terminal of the first transistor Q10. When the voltage switching signal output pin P2.7 of the control unit U1 is in a high-impedance state (e.g., during power-on reset or program initialization), the potential of the first input terminal of the first transistor Q10 is stably pulled down to ground level, ensuring that it is in a reliable cut-off state, thereby preventing the relay RE1 from being activated due to false triggering and improving the circuit's anti-interference capability.

[0032] The control unit U1 outputs a high-level or low-level signal through the voltage switching signal output pin P2.7 to control the conduction or cutoff of the first transistor Q10. When the control unit U1 needs to switch the output voltage, it outputs a high-level signal. This signal, after passing through the first driving current-limiting resistor R11, drives the first transistor Q10 from the cutoff state to the saturated conduction state. After the first transistor Q10 is turned on, a low-impedance path is formed between its collector and emitter, energizing the coil of the relay RE1 and generating a magnetic field to close the contacts, thereby realizing the switching from the first rated voltage (e.g., 12V) to the second rated voltage (e.g., 24V). When the control unit U1 outputs a low-level signal, the first transistor Q10 is turned off, the relay RE1 coil is de-energized, and its contacts return to the normally closed state under the action of the spring, restoring the output to the first rated voltage.

[0033] In one embodiment, the driving circuit further includes a freewheeling diode D18, a second transistor Q8, a first capacitor EC10, and a first Zener diode ZD2; the anode of the freewheeling diode D18 is connected to the first terminal of the first transistor Q10, the cathode of the freewheeling diode D18 is connected to a DC power supply, the first input terminal of the second transistor Q8 is connected to the cathode of the first Zener diode ZD2, the anode of the first Zener diode ZD2 is grounded, and the second terminal of the second transistor Q8 is grounded through the first capacitor EC10.

[0034] When the first transistor Q10 changes from the on state to the off state, the relay RE1 coil generates a high-voltage reverse electromotive force due to the sudden change in current. This electromotive force forms a discharge circuit through the freewheeling diode D18, thereby releasing the magnetic energy stored in the coil back to the power supply or consuming it, effectively suppressing the high voltage breakdown of the first transistor Q10 and improving circuit safety.

[0035] In one embodiment, the first input terminal and the first connection terminal of the second transistor Q8 are also connected in parallel through a resistor.

[0036] In this embodiment, the voltage switching signal output by the control unit U1 controls the conduction or cutoff of the first transistor Q10, thereby changing the relay RE1 device to achieve automatic switching of the rated voltage output, achieving the effect of adaptive matching of LED load 6, and avoiding problems such as LED damage caused by manual selection of output voltage errors.

[0037] In one embodiment, the voltage output module 4 includes a first driver chip U5, a third transistor Q9, a fourth transistor Q2, a third current-limiting resistor R13, a fourth current-limiting drive resistor R21, a second capacitor C11, and a second Zener diode ZD1. The PWM signal output pin PWM12 of the control unit U1 is connected to the input pin of the first driver chip U5 through the third current-limiting resistor R13, and the output pin of the first driver chip U5 is connected to the first input terminal of the third transistor Q9 through the fourth current-limiting drive resistor R21. The second connection terminal of the fourth transistor Q2 is connected to the power supply pin of the first driver chip U5, and the second connection terminal of the fourth transistor Q2 is also grounded through the second capacitor C11. The cathode of the second Zener diode ZD1 is connected to the first input terminal of the fourth transistor Q2, and the anode of the second Zener diode ZD1 is grounded. The first connection terminal of the third transistor Q9 is connected to the output terminal of the voltage switching module 5, and the second connection terminal of the third transistor Q9 is connected to both the voltage output module 4 and the LED load 6. In one embodiment, the first connection terminal of the third transistor Q9 is connected to the output terminal of the relay RE1.

[0038] The first driver chip U5 receives the PWM signal output by the control unit U1, and controls the third transistor Q9 to be turned on or off according to the PWM signal, thereby controlling the on or off of the output voltage.

[0039] In one embodiment, the first driver chip U5 is an N531 chip.

[0040] In one embodiment, the third transistor Q9 is a MOSFET, specifically an N-channel MOSFET. The first input terminal, first connection terminal, and second connection terminal of the third transistor Q9 are the gate, source, and drain, respectively. The third transistor Q9 is the primary power switching element. The control unit U1 outputs a PWM signal to the first driver chip U5. The first driver chip U5 processes the signal and outputs it to the third transistor Q9. By controlling the voltage at the first input terminal of the third transistor Q9, it switches between an on and off state, thereby controlling the output voltage to turn on and off.

[0041] In one embodiment, when a short circuit is detected at the output terminal, the control unit U1 outputs a PWM signal to control the voltage output module 4, causing the third transistor Q9 to be turned off, thereby controlling the output voltage to be zero.

[0042] In one embodiment, the voltage output module 4 further includes an optocoupler isolation unit, the input terminal of which is connected to the first pin AIN7 of the control unit U1, and the output terminal of which is connected to the voltage switching module 5; The optocoupler isolation unit is used to receive the isolation signal output by the control unit U1 and perform electrical isolation.

[0043] The optocoupler isolation unit includes an optocoupler OPT1, which is a semiconductor device that uses light as a medium to transmit electrical signals. It consists of a light-emitting diode and a phototransistor and is used to achieve electrical isolation between the input and output circuits.

[0044] In this embodiment, voltage output control is achieved by connecting the third transistor Q9 to the output terminal of the voltage switching module 5 and controlling the conduction or cutoff of the third transistor Q9 by the PWM signal output by the control unit U1.

[0045] The voltage detection module 2 includes a voltage comparison circuit, which includes a detection diode. The ground terminal of the voltage comparison circuit is connected to the normally closed contact and normally open contact of the input relay RE1, and is connected to the first power supply winding and the second power supply winding, respectively. The voltage comparison circuit of the voltage detection module 2 is connected to the second connection terminal of the third transistor Q9 through the detection diode.

[0046] The voltage comparison circuit is connected to the pin of the control unit U1 through a series resistor, and the other end is connected to the output terminal of the voltage output module 4, specifically to the second connection terminal of the third transistor Q9. The voltage comparison circuit is used to determine the short circuit of the output terminal when the device is powered on and initialized.

[0047] In one embodiment, the voltage comparison circuit includes two sets of detection diodes connected in parallel, respectively connected to the two voltage comparison pins P1.2 and TX of the control unit U1. In another embodiment, the voltage comparison circuit may also include only one set of detection diodes connected to one of the voltage comparison pins of the control unit U1.

[0048] The control unit U1 controls the voltage output module 4 to output a test voltage. The voltage comparison circuit obtains the sampled comparison voltage values ​​at the first connection terminal (source) and the second connection terminal (drain) when the third transistor Q9 is disconnected. When the sampled comparison voltage value is lower than the preset voltage threshold, it is determined that there is no short circuit at the output terminal; otherwise, it is determined that there is a short circuit at the output terminal.

[0049] In one embodiment, when the third transistor Q9 is turned off, a test voltage (e.g., 5V) is output to the voltage comparison circuit to collect the current value of the detection diode. If the current value is 0 or less than a preset threshold, it is determined that no short circuit has occurred; otherwise, it is determined that a short circuit has occurred.

[0050] In one embodiment, after device initialization, the control unit U1 controls the voltage output module 4 to output a test voltage (e.g., 5V) lower than the LED lamp conduction voltage (e.g., 7V). The control unit U1 compares the sampled voltage values ​​across the first connection terminal (source) and the second connection terminal (drain) when the third transistor Q9 is disconnected through the voltage comparison circuit. If there is no short circuit at the output terminal, the sampled voltage value is less than a preset voltage threshold, and the control unit U1 obtains a low level result, determining that the output terminal can operate normally and can proceed with the subsequent process of providing working voltage to the LED load 6. If there is a short circuit at the output terminal, the voltage across the first connection terminal (source) and the second connection terminal (drain) is pulled down to near 0V due to the short circuit at the output terminal, or a large current is generated due to the extremely small loop impedance, causing the output of the second connection terminal of the third transistor Q9 to be abnormal, thereby determining that the output terminal is short-circuited, and then the control unit U1 outputs a PWM signal to control the third transistor Q9 to be cut off, making the output voltage zero.

[0051] In one embodiment, when the detected sampled voltage value is greater than a preset threshold, the PWM signal output pin PWM12 of the control unit U1 outputs a high-level signal and controls the output voltage to the first rated voltage. The current sampled through the sampling resistor RS2 is input to the operational amplifier U2 and then to the control unit U1. When the detected value is greater than the set amplitude of the initial stable value, it is initially determined that there is a suspected output short circuit. After repeating this process multiple times, if the detected value is greater than the set amplitude of the initial stable value, it is determined that the output terminal is in a short circuit state. Then, the PWM signal output pin PWM12 outputs a low-level signal to turn off the third transistor Q9 and restart the power supply to perform the initial short circuit detection.

[0052] This embodiment obtains and compares the voltage samples across the first connection terminal (Source) and the second connection terminal (Drain) when the third transistor Q9 is disconnected, and compares them with a preset threshold, thereby determining whether there is a short circuit fault in the output terminal line at the initial stage of power-on, effectively improving the safety and reliability of the circuit.

[0053] In one embodiment, the voltage detection module 2 further includes a first voltage divider resistor R25, a second voltage divider resistor R20, and a fifth capacitor C15; the voltage detection pin AIN3 of the control unit U1 is connected to the output terminal of the voltage output module 4 through the first voltage divider resistor R25, and the voltage detection pin AIN3 of the control unit U1 is also grounded through the second voltage divider resistor R20 and the fifth capacitor C15 respectively.

[0054] The voltage detection pin AIN3 of the control unit U1 is also connected to a voltage divider sampling circuit for real-time detection of the output voltage.

[0055] The first voltage divider and the second voltage divider form a resistor voltage divider network. Based on the voltage divider law of series resistors, the higher output voltage is proportionally reduced to a lower voltage value. The safe voltage value after voltage division is input to the control unit U1 through the voltage detection pin AIN3.

[0056] In this embodiment, the output voltage is obtained through the voltage detection pin AIN3 to achieve real-time detection of the output voltage.

[0057] In one embodiment, the current detection module 3 includes a sampling resistor RS2, an operational amplifier U2, a first resistor R23, a second resistor R22, a third resistor R18, a fifth current-limiting resistor R19, a third capacitor C12, and a fourth capacitor C13. The sampling resistor RS2 is disposed between the voltage output module 4 and the voltage switching module 5. The non-inverting input terminal of the operational amplifier U2 is connected to the output terminal of the sampling resistor RS2 through the first resistor R23. The non-inverting input terminal of the operational amplifier U2 is also grounded through the third capacitor C12. The inverting input terminal of the operational amplifier U2 is connected to the output terminal of the operational amplifier U2 through the second resistor R22. The fourth capacitor C13 is connected in parallel between the inverting input terminal and the output terminal of the operational amplifier U2. The inverting input terminal of the operational amplifier U2 is also grounded through the third resistor R18. The output terminal of the operational amplifier U2 is connected to the current detection pin of the control unit U1 through the fifth current resistor R19. The output current passes through the sampling resistor RS2 and is converted into a voltage signal, which is then input to the operational amplifier U2. After being amplified by the operational amplifier U2, the signal is input to the control unit U1.

[0058] The sampling resistor RS2 is a current sensing resistor with precise resistance and strong power handling capability, and is set between the voltage output module 4 and the voltage switching module 5, that is, connected in series in the main power output circuit.

[0059] In one embodiment, the output terminal of the relay RE1 of the voltage output module 4 is connected to the second connection terminal of the third transistor Q3 through the sampling resistor RS2.

[0060] The inverting input terminal of the operational amplifier U2 is connected to the output terminal of the operational amplifier U2 through the second resistor R22, forming a negative feedback network. The fourth capacitor C13 is connected in parallel between the inverting input terminal and the output terminal of the operational amplifier U2 for phase compensation, preventing circuit self-oscillation and enhancing stability.

[0061] The current detection module 3 forms a non-inverting operational amplifier U2 structure. When the output current flows through the sampling resistor RS2, a weak voltage signal is generated at its two ends. This voltage signal is sent to the non-inverting input terminal of the operational amplifier U2 through the first resistor R23 to linearly amplify the voltage signal. The amplified signal is then input to the current detection pin of the control unit U1.

[0062] In this embodiment, the current signal of the sampling resistor RS2 is detected, converted into a voltage signal, and amplified by the operational amplifier U2 to provide a stable and reliable current feedback signal to the control unit U1, thereby achieving accurate load current identification.

[0063] In one embodiment of the solution provided in this application, the first rated voltage is 12V, the second rated voltage is 24V, and the rated voltage of the LED load is 24V. The automatic identification and voltage switching process after power-on is as follows: When the device is powered on, the control unit completes initialization. First, the control unit performs an initial short-circuit detection: it controls the third transistor (Q9) to turn off and monitors the output status through its dedicated detection pin (P1.2) and the current detection module (sampling resistor RS2). After confirming that no short-circuit fault is detected, the control unit enters the voltage identification process.

[0064] The control unit first controls the relay (RE1) in the voltage switching module to connect the 12V winding and drive Q9 to conduct, outputting a 12V voltage to the output terminal. Since the rated operating voltage of the LED load is 24V, it cannot light up at 12V, so the loop current is extremely small. Within a preset time period after the 12V voltage is output (e.g., 100ms, 300ms, etc.), if the current value sampled by the current detection module by the control unit remains below the preset load activation threshold, the control unit determines that the 12V voltage is mismatched with the load.

[0065] Subsequently, the control unit performs a safety switching operation: First, it controls Q9 to turn off, cutting off the 12V voltage output; then, it controls relay (RE1) to activate, switching its contacts from the 12V winding to the 24V winding; finally, it controls Q9 to turn on again, applying 24V voltage to the LED load. Since the 24V voltage matches the rated voltage of the LED load, the load is lit normally, and a normal operating current is generated in the circuit. The control unit confirms through the current detection module that the current value is within the normal range, thus determining that the voltage matching is successful, and enters a stable operation and continuous monitoring state.

[0066] The LED constant voltage control circuit provided in this application embodiment, after the device is powered on, the control unit controls the voltage output module to output a test voltage (e.g., 5V) lower than the LED lamp conduction voltage (e.g., 7V). The control unit compares the sampled voltage values ​​at the first connection terminal (source) and the second connection terminal (drain) when the third transistor is disconnected through the voltage comparison circuit. If there is no short circuit at the output terminal, the sampled voltage value is less than a preset voltage threshold, and the control unit obtains a low level result, determining that the output terminal can operate normally and can proceed with the subsequent process of providing working voltage to the LED load; if a short circuit occurs at the output terminal, the first connection terminal (source)... If the voltage across the second connection terminal (drain) is pulled down to near 0V due to a short circuit at the output terminal, or if a large current is generated due to extremely low circuit impedance, the output of the second connection terminal of the third transistor will be abnormal. This indicates a short circuit at the output terminal, prompting the control unit to output a PWM signal to control the third transistor to cut off (open circuit), making the output voltage zero. If no short circuit is detected at the output terminal, the control unit controls the voltage switching module to adjust the relay position in the voltage switching module, connecting the relay to the first rated voltage (e.g., 12V), simultaneously driving the third transistor to conduct, outputting the first rated voltage to the LED load through the third transistor. After outputting the first rated voltage... The control unit detects the current and voltage values ​​of the sampling resistor to monitor the load circuit current. If the detected current value is within the normal operating current range of the LED, the rated voltage of the LED load matches the current first rated voltage, and the control unit maintains the current first rated voltage value to ensure stable LED illumination. If no current is detected (or the current value is extremely small) within a preset time, it is determined that the current first rated voltage is lower than the rated voltage of the LED load. The control unit controls the third transistor to turn off, opening the third transistor, shutting off the output, and driving the relay in the voltage switching module to adjust the position, connecting the relay to the second rated voltage (e.g., 24V). After the switching is completed, the control unit... The control unit controls the third transistor to turn on again, outputting the second rated voltage to the LED load through the third transistor. After different rated voltages are output through the voltage switching module and voltage matching is completed, the LED load is in a stable working state. The control unit continuously samples the current and voltage values ​​of the sampling resistor, records an initial stable value, and presets the change range to obtain a stable operating range value and determine the safe current threshold. If the detected current exceeds the preset safe current threshold, it is initially determined that there is a short circuit suspicion. After multiple cycles, if the detected current is greater than the set range of the initial stable value, it is determined that the output terminal is in a short circuit state. The control unit controls the third transistor to turn off and restarts the power supply to re-execute the initial short circuit detection process.If a short circuit is detected again during the short circuit detection after restarting, the circuit is determined to have a short circuit fault. The control unit then controls the third transistor to remain in the off state until the short circuit fault is cleared.

[0067] The circuit provided in this application achieves seamless automatic identification of the rated voltage of the LED load by first outputting a safe low voltage for short-circuit pre-detection, and then intelligently matching different rated voltages in a stepped manner while detecting the load current. This completely solves the problem of equipment mismatch caused by manual configuration errors. Simultaneously, by monitoring changes in electrical parameters throughout the entire process from initial startup to stable operation, it can promptly and accurately identify short-circuit faults in remote lines or loads and immediately take shutdown protection measures, fundamentally eliminating the risk of wire overheating and fire caused by short-circuit current. This application represents a dual breakthrough in the convenience and safety of LED constant voltage control devices, significantly improving the product's intelligence and reliability.

[0068] Secondly, embodiments of this application provide an LED device, including the LED constant voltage circuit as described in the above embodiments.

[0069] The structure of the LED device described in this embodiment is roughly the same as that of the LED constant voltage circuit described in the above embodiments. For details, please refer to the LED constant voltage circuit provided in the above embodiments, which will not be repeated here.

[0070] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. An LED constant voltage control circuit, characterized in that, It includes a control unit, a voltage detection module, a current detection module, a voltage output module, a voltage switching module, and an LED load; The voltage detection module and the current detection module are respectively connected to the control unit; wherein, the voltage detection module is used to detect the output voltage, and the current detection module is used to detect the output current, and respectively feeds back the detection signals to the control unit; The voltage output module is connected to the control unit, the output terminal of the voltage switching module, and the LED load, respectively; wherein, the voltage output module is used to output voltage to the LED load, and control the output voltage to be turned on or off according to the PWM signal output by the control unit; The voltage switching module is connected to the control unit. The input terminal of the voltage switching module is connected to at least two power windings that can provide different rated voltages, and the output voltage is switched according to the voltage switching signal output by the control unit.

2. The LED constant voltage control circuit according to claim 1, characterized in that, The voltage switching module includes a relay, a drive circuit, a first power winding, and a second power winding. The coil of the relay is connected to the control unit through the drive circuit. The normally closed contact and normally open contact of the relay are respectively connected to the first power winding and the second power winding. The first power winding is used to output a first rated voltage, and the second power winding is used to output a second rated voltage. The first rated voltage and the second rated voltage are different.

3. The LED constant voltage control circuit according to claim 2, characterized in that, The driving circuit includes a first transistor, a first driving current-limiting resistor, a second current-limiting resistor, and a first pull-down resistor; the first input terminal of the first transistor is connected to the voltage switching signal output pin of the control unit through the first driving current-limiting resistor, the first connection terminal of the first transistor is connected to one end of the coil of the relay through the second current-limiting resistor, the second connection terminal of the first transistor is grounded, and the two ends of the first pull-down resistor are respectively connected to the first input terminal and the second connection terminal of the first transistor. The voltage switching signal output by the control unit controls the first transistor to turn on or off, thereby controlling the relay to switch the output voltage between the first rated voltage and the second rated voltage.

4. The LED constant voltage control circuit according to claim 3, characterized in that, The driving circuit further includes a freewheeling diode, a second transistor, a first capacitor, and a first Zener diode; the anode of the freewheeling diode is connected to the first terminal of the first transistor, the cathode of the freewheeling diode is connected to a DC power supply, the first input terminal of the second transistor is connected to the cathode of the first Zener diode, the anode of the first Zener diode is grounded, and the second terminal of the second transistor is grounded through the first capacitor.

5. The LED constant voltage control circuit according to claim 1, characterized in that, The voltage output module includes a first driver chip, a third transistor, a fourth transistor, a third current-limiting resistor, a fourth current-limiting drive resistor, a second capacitor, and a second Zener diode. The PWM signal output pin of the control unit is connected to the input pin of the first driver chip through the third current-limiting resistor, and the output pin of the first driver chip is connected to the first input terminal of the third transistor through the fourth current-limiting drive resistor. The second connection terminal of the fourth transistor is connected to the power supply pin of the first driver chip, and the second connection terminal of the fourth transistor is also grounded through the second capacitor. The cathode of the second Zener diode is connected to the first input terminal of the fourth transistor, and the anode of the second Zener diode is grounded. The first connection terminal of the third transistor is connected to the output terminal of the voltage switching module. The second connection terminal of the third transistor is connected to both the voltage output module and the LED load. The first driver chip receives the PWM signal output by the control unit and controls the third transistor to turn on or off according to the PWM signal, thereby controlling the output voltage to be turned on or off.

6. The LED constant voltage control circuit according to claim 5, characterized in that, The voltage output module also includes an optocoupler isolation unit, the input terminal of which is connected to the first pin of the control unit, and the output terminal of which is connected to the voltage switching module. The optocoupler isolation unit is used to receive the isolation signal output by the control unit and perform electrical isolation.

7. The LED constant voltage control circuit according to claim 5, characterized in that, The voltage detection module includes a voltage comparison circuit, which includes a detection diode. The voltage comparison pin of the control unit is connected to the second connection terminal of the third transistor through the detection diode. The control unit controls the voltage output module to output a test voltage, and samples the sampled voltage value output by the third transistor through the voltage comparison circuit. When the sampled voltage value is lower than the preset voltage threshold, it is determined that no short circuit or open circuit has occurred at the output terminal; otherwise, it is determined that the output terminal is short-circuited.

8. The LED constant voltage control circuit according to claim 1, characterized in that, The current detection module includes a sampling resistor, an operational amplifier, a first resistor, a second resistor, a third resistor, a fifth current-limiting resistor, a third capacitor, and a fourth capacitor; The sampling resistor is disposed between the voltage output module and the voltage switching module. The non-inverting input terminal of the operational amplifier is connected to the output terminal of the sampling resistor through the first resistor. The non-inverting input terminal of the operational amplifier is also grounded through the third capacitor. The inverting input terminal of the operational amplifier is connected to the output terminal of the operational amplifier through the second resistor. The fourth capacitor is connected in parallel between the inverting input terminal and the output terminal of the operational amplifier. The inverting input terminal of the operational amplifier is also grounded through the third resistor. The output terminal of the operational amplifier is connected to the current detection pin of the control unit through the fifth current limiting resistor. The output current passes through the sampling resistor and is converted into a voltage signal, which is then input to the operational amplifier. After being amplified by the operational amplifier, the signal is input to the control unit.

9. The LED constant voltage control circuit according to claim 1, characterized in that, The voltage detection module further includes a first voltage divider resistor, a second voltage divider resistor, and a fifth capacitor; the voltage detection pin of the control unit is connected to the output terminal of the voltage output module through the first voltage divider resistor, and the voltage detection pin of the control unit is also grounded through the second voltage divider resistor and the fifth capacitor respectively.

10. An LED device, characterized in that, Includes the LED constant voltage control circuit as described in any one of claims 1-9.

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