Constant-voltage LED drive circuit

Abstract

The utility model provides a constant voltage LED drive circuit comprising an MCU, a filter rectification module, a PFC module, an LLC module, a secondary side synchronous rectification module, and an optocoupler isolation feedback module. The filtering and rectifying module is connected with alternating current and converts the alternating current into direct current, the PFC module is connected with the output end of the filtering and rectifying module, the filtering and rectifying module supplies power to the PFC module, and the PFC module is used for power factor correction. The LLC module is connected with the output end of the PFC module and the MCU, the PFC module supplies power to the LLC module, and the MCU controls the LLC module to further convert direct current output by the PFC module into direct current voltage required by a load. And the secondary side synchronous rectification module is connected with the output end of the LLC module and is used for carrying out output rectification on an output power supply of the LLC module, so that the output power supply is supplied to a load LED. And the optocoupler isolation feedback module is connected with the output end of the secondary side synchronous rectification module and the MCU, samples the output voltage of the secondary side synchronous rectification module and feeds back the output voltage to the MCU, so that the MCU controls the LLC module to adjust the output voltage, thereby realizing constant voltage output.

Description

TECHNICAL FIELD

[0001] The utility model relates to LED drive power supply technical field, especially a kind of constant voltage LED drive circuit. BACKGROUND

[0002] With the rapid development of lighting technology, LED (Light Emitting Diode) has gradually become the mainstream choice in the lighting field due to its high efficiency, long life, environmental protection and energy saving, etc. In the LED lighting system, the drive power as a key component, its performance directly affects the luminous efficiency, stability and service life of LED lamps. At present, the mainstream LED driving mode in the market is mainly divided into two categories: constant voltage drive and constant current drive.

[0003] Constant current drive effectively deals with the characteristics of LED changing with voltage by controlling constant current, ensuring the brightness consistency of LED under different working conditions. However, when multiple LED light sources are used in parallel with constant current drive, if one or more light sources fail due to failure, the current of the remaining light sources may increase due to the decrease of total resistance, thereby accelerating the aging process of these light sources, affecting the stability and life of the whole lamp. In addition, constant current drive usually requires customized lamp panel design, once the whole lamp fails, ordinary users are difficult to replace directly, increasing the maintenance cost and difficulty.

[0004] In contrast, constant voltage drive has significant advantages in multi-path light source parallel application due to its stable voltage, safety and reliability. Constant voltage drive system is generally designed to output low voltage such as 12V or 24V, which not only improves the safety of use, but also facilitates the direct parallel connection of multiple light sources, simplifying the circuit design. More importantly, unlike constant current drive, each light source in constant voltage drive system is usually equipped with a constant current control mechanism, which means that even if a light source is damaged, it will not affect the brightness of other light sources, thereby ensuring the uniformity and stability of the whole lamp lighting.

[0005] However, although constant voltage drive performs well in many aspects, it still needs to be continuously optimized in practical application to improve its adaptability and efficiency, and to provide LED lamps with high-quality, stable drive power without flicker and safety isolation. UTILITY MODEL CONTENTS

[0006] In order to solve the above problems, the purpose of the utility model is to provide a constant voltage LED drive circuit, which samples the output voltage, and feeds back the secondary output signal to MCU through optical coupling isolation circuit by control signal, and MCU controls LLC module to further convert the direct current output by PFC module into direct current voltage required by load, so as to realize constant voltage output.

[0007] The utility model realizes the following technical scheme:

[0008] A constant voltage LED driving circuit, comprising:

[0009] MCU;

[0010] A filter rectifier module is used for accessing alternating current and converting it into direct current;

[0011] A PFC module is connected with the output end of the filter rectifier module, the filter rectifier module is used for supplying power for the PFC module, and the PFC module is used for power factor correction;

[0012] An LLC module is connected with the PFC module and the MCU, the PFC module is used for supplying power for the LLC module, and the MCU controls the LLC module to further convert the direct current output by the PFC module into a direct current voltage with a size required by a load;

[0013] A secondary side synchronous rectification module is connected with the output end of the LLC module and is used for output rectification of the power supply output by the LLC module, so as to supply the load LED;

[0014] An optocoupler isolation feedback module is connected with the output end of the secondary side synchronous rectification module and the LLC module, is used for sampling the output voltage of the secondary side synchronous rectification module, and feeds back to the MCU.

[0015] Further, a constant voltage LED driving circuit further comprises:

[0016] A DALI module is connected with a D4i host and is used for accepting and transmitting the signal sent by the D4i host;

[0017] A digital signal processor is connected with the DALI module and is used for receiving and processing the dimming signal sent by the DALI module;

[0018] A constant voltage dimming control module is connected between the output end of the secondary side synchronous rectification module and the load LED, and is further connected with the digital signal processor and is used for dimming the load LED according to the dimming signal;

[0019] A power supply module is connected with the output end of the secondary side synchronous rectification module, and is further connected with the digital signal processor and the constant voltage dimming control module, and is used for supplying power for the digital signal processor and the constant voltage dimming control module.

[0020] Compared with the prior art, the technical scheme and beneficial effects of the utility model are as follows:

[0021] (1) The utility model discloses filter rectifier module is accessed to alternating current and is converted to direct current, and power is supplied for PFC module, and PFC module is used for power factor correction, and PFC module is for LLC module power supply, and MCU controls LLC module to further convert the direct current of PFC module output into the direct current voltage of the size required by load, and the output rectifier module of auxiliary side synchronous rectification carries out output rectification to LLC module power supply, thereby supply to load LED, and the output voltage of the output rectifier module of auxiliary side synchronous rectification is sampled to light coupling isolation feedback module, and is fed back to MCU, and make MCU control LLC module to adjust output voltage, thereby realizing constant voltage output. Meanwhile, the framework of PFC+LLC is adopted, and when full load output, can realize high efficiency in wide load range.

[0022] (2) The utility model discloses constant voltage LED drive circuit still includes DALI module, digital signal processor and constant voltage light control module, and accesses D4i host computer. D4i host computer and load between two -way communication, realizes remote light control, intelligent light control, and is convenient for accessing various light control systems.

[0023] (3) The protection module between the digital signal processor of the utility model and constant voltage light control module can quickly and effectively detect load short circuit, open circuit and overload and other abnormal conditions, and feed back the abnormal condition to D4i host computer, and detect and protect the circuit. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 It is the principle block diagram of constant voltage LED drive circuit provided by the utility model embodiment;

[0025] Figure 2 It is the circuit principle diagram of filter rectifier module provided by the utility model embodiment;

[0026] Figure 3 It is the circuit principle diagram of PFC module provided by the utility model embodiment;

[0027] Figure 4 It is the circuit principle diagram of LLC module provided by the utility model embodiment;

[0028] Figure 5 It is the circuit principle diagram of the output rectifier module of auxiliary side synchronous rectification provided by the utility model embodiment;

[0029] Figure 6 It is the circuit principle diagram of light coupling isolation feedback module provided by the utility model embodiment;

[0030] Figure 7 It is the circuit principle diagram of DALI module provided by the utility model embodiment;

[0031] Figure 8A circuit principle diagram of a power supply module is provided in the embodiment of the utility model.

[0032] Figure 9 A circuit principle diagram of a digital signal processor is provided in the embodiment of the utility model.

[0033] Figure 10 A circuit principle diagram of a constant-voltage dimming control module is provided in the embodiment of the utility model. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical scheme and advantages of the embodiments of the utility model clearer, the technical scheme in the embodiments of the utility model will be described clearly and completely below with reference to the drawings in the embodiments of the utility model. Obviously, the described embodiments are part of the embodiments of the utility model, rather than all the embodiments. It should be understood that the specific embodiments described herein are only used to explain the utility model, and are not used to limit the utility model. Based on the embodiments in the utility model, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the utility model.

[0035] Referring to Figure 1 A constant-voltage LED driving circuit includes an MCU, a filter rectifier module, a PFC module, an LLC module, a secondary side synchronous rectification module and an optocoupler isolation feedback module. The filter rectifier module is connected to an alternating current and converts the alternating current into a direct current. The PFC module is connected to an output end of the filter rectifier module, and the filter rectifier module supplies power to the PFC module. The PFC module is used for power factor correction. The LLC module is connected to an output end of the PFC module and the MCU, and the PFC module supplies power to the LLC module. The MCU controls the LLC module to further convert the direct current output by the PFC module into a direct current voltage of a required size for a load. The secondary side synchronous rectification module is connected to an output end of the LLC module and rectifies the output power of the LLC module to supply the load LED. The optocoupler isolation feedback module is connected to an output end of the secondary side synchronous rectification module and the MCU, samples the output voltage of the secondary side synchronous rectification module and feeds back to the MCU, so that the MCU controls the LLC module to adjust the output voltage, thereby realizing constant-voltage output.

[0036] Continuing to refer to Figure 1The constant-voltage LED driving circuit further comprises a DALI module, a digital signal processor and a constant-voltage dimming control module. The DALI module is connected with the D4i host and is used for receiving and transmitting signals sent by the D4i host. The digital signal processor is connected with the DALI module and is used for receiving and processing dimming signals sent by the DALI module and outputting dimming control signals. The constant-voltage dimming control module is connected between an output end of the secondary side synchronous rectification module and the load LED, and is further connected with the digital signal processor and is used for dimming the load LED according to the dimming control signals. The digital signal processor and the constant-voltage dimming control module are both connected with the power supply module, and the power supply module supplies power for the digital signal processor and the constant-voltage dimming control module.

[0037] The driving circuit of the embodiment integrates the two dimming modes of D4i and PUSH. The driving circuit has good compatibility, is convenient to access various dimming systems and can realize intelligent dimming. The dimming circuit framework adopts the D4i protocol, has strong communication capability, realizes bidirectional communication, has no polarity requirement in wiring and has no limitation on network wiring topology (star type, tree type, ring type and mixed type are all available). In terms of functions, grouping and scene setting can be realized through the host, so that products produced by different lighting equipment manufacturers are seamlessly interconnected.

[0038] Referring to Figure 2 The filter rectification module comprises a surge protection component, an EMC filter component and a rectification component. The fuse F1 is connected in series with the live wire access line. When an abnormal short circuit occurs in the circuit, a great current is generated instantaneously, and the fuse F1 can be fused rapidly to prevent the current from continuing to flow and to avoid causing more serious electrical accidents. The voltage-dependent resistor RV1 is connected in parallel between the live wire access line and the zero wire access line and can absorb the energy of transient overvoltage and convert most of the energy into heat energy to dissipate. When the voltage across the two ends is lower than the threshold voltage, the resistance value of the voltage-dependent resistor RV1 is very high, which is equivalent to an open circuit. When the voltage across the two ends exceeds the threshold voltage, the resistance value of the voltage-dependent resistor RV1 will decrease sharply to allow the current to pass through, so as to clamp the overvoltage at a safe level and protect the circuit from damage caused by overvoltage. The voltage-dependent resistor RV1 can pass the lightning protection test of differential mode 2KV and common mode 2KV.

[0039] The thermistor NTC1 is connected in series with the positive input line. When the power supply device is just started, the thermistor NTC1 is in a room temperature state, and the resistance value of the thermistor NTC1 is relatively high at this time. The high resistance value can reduce the driving impact current. The high-voltage thin-film capacitor CX1, the high-voltage thin-film capacitor CX2, the capacitor C1, the capacitor C2, the common-mode inductor LF1, the common-mode inductor LF2, the common-mode inductor LF3 and the inductor L1 provide EMC filtering and AC rectification for the circuit.

[0040] Referring to Figure 3The PFC module comprises a power factor control chip U1, a switch tube Q1, a common-mode inductor L2, a diode D3, a diode D4, an electrolytic capacitor CE1, the common-mode inductor L2 and the diode D3 are connected in series between the filter rectifier module and the LLC module, the diode D4 is connected in parallel between two ends of the common-mode inductor L2 and the diode D3 away from each other, the cathode of the diode D3 is connected with the LLC module, the electrolytic capacitor CE1 is connected between the cathode end of the diode D3 and the negative electrode, the control end of the switch tube Q1 is connected with the DRV pin of the power factor control chip U1, and the two electrode ends of the switch tube Q1 are respectively connected between the common end of the common-mode inductor L2 and the diode D3 and the CS pin of the power factor control chip U1. In the embodiment, the power factor control chip U1 adopts NCL2801.

[0041] A PWM square wave is output by the power factor control chip U1 to control the switching of the switch tube Q1, and the constant voltage is provided for the LLC module by the common-mode inductor L2, the diode D4, the diode D3, the electrolytic capacitor CE1 and other power devices. Meanwhile, the input current waveform of the PFC module is shaped by the signals collected by the resistance R34, the resistance R35, the resistance R36, the resistance R19 and the capacitor C9 connected to the output end of the filter rectifier module, the active power is improved, and the harmful odd harmonics are reduced. The current signal of the switch tube Q1 is sampled by the resistance R4 to provide overcurrent protection for the power factor control chip U1.

[0042] Referring to Figure 4 The LLC module comprises a resonant inductor L6, a transformer primary winding TR1C and a resonant capacitor C5 forming a loop with the output end of the filter rectifier module, further comprises a second switch tube Q2 with two electrode ends connected in series between the output end of the filter rectifier module and the resonant inductor L6, and a third switch tube Q3 with two electrode ends connected in parallel between two ends of the resonant inductor L6 and the resonant capacitor C5 away from each other, and the control ends of the second switch tube Q2 and the third switch tube Q3 are connected with the power supply driving chip U2.

[0043] The resonant network is composed of the resonant inductor L6, the transformer primary winding TR1C and the resonant capacitor C5, the second switch tube Q2 and the third switch tube Q3 are turned on alternately near the resonant frequency Fr, and can be turned on under the condition of zero voltage, so that the switch tube in the secondary side synchronous rectification module can realize zero current switching. The switching is realized through the resonant network, which can greatly reduce the switching loss and improve the overall efficiency. The output voltage of the LLC module is controlled by adjusting the switching frequency, and above the resonant frequency, the output voltage will decrease with the increase of the frequency; below the resonant frequency, the output voltage will increase with the decrease of the frequency. This frequency control mechanism enables the LLC module to maintain high efficiency in a wide load range, and the resonant network can adaptively adjust its working point to maintain the optimal state close to soft switching, so as to maintain high efficiency in a wide load range.

[0044] The LLC module further comprises an over-voltage protection component, an over-temperature protection component, an over-power protection component, etc. The diode D12, the resistor R45, and the capacitor C20 provide a driving voltage for the second switch tube Q2. The Zener diode ZD4 and the Zener diode ZD2 provide over-voltage protection for the circuit. The temperature sensing resistor NTC2 and the resistor R39 are used for temperature acquisition of the power supply driving chip U2, and over-temperature protection can be achieved. The resistor R40, the resistor R43, the resistor R44, the capacitor C17, the capacitor C18, the capacitor C19, and the capacitor C25 are used for acquiring a resonance current, and over-power protection is provided for the resonance module.

[0045] Referring to Figure 5 The secondary side synchronous rectification module comprises a synchronous rectification chip, a rectification bridge, and a filter capacitor set. The synchronous rectification chip is connected to the power supply module. The filter capacitor set is connected in parallel between the output end of the secondary side synchronous rectification module and the ground. The rectification bridge comprises at least four field effect tubes. In this embodiment, the filter capacitor set comprises the electrolytic capacitor CE6 and the electrolytic capacitor CE7. The rectification bridge comprises the MOSFET tube Q8, the MOSFET tube Q9, the MOSFET tube Q10, and the MOSFET tube Q11. The output rectification is achieved through the transformer TR1 output winding TR1A, the output winding TR1B, the MOSFET tube Q8, the MOSFET tube Q9, the MOSFET tube Q10, the MOSFET tube Q11, the electrolytic capacitor CE6, and the electrolytic capacitor CE7. The synchronous rectification chip U4 is the synchronous rectification chip SRK2001. Since the on-resistance (Rds(on)) of the MOSFET tube Q8, the MOSFET tube Q9, the MOSFET tube Q10, and the MOSFET tube Q11 is much lower than the forward voltage drop of a traditional diode, the synchronous rectification can significantly reduce the on-resistance loss and improve the efficiency under the same large current condition. The use of MOSFET instead of diode rectification can reduce the on-resistance loss of the secondary side. The resistor R51 and the resistor R57 are used for discharging the current at the GS poles of the MOSFET tube Q9 and the MOSFET tube Q10. The capacitor C28 provides filtering for the VCC pin of the synchronous rectification chip U4. When the D-S voltage difference is greater than the set value of the synchronous rectification chip U4, the MOSFET tube Q9 and the MOSFET tube Q10 are turned on by the resistor R50 and the resistor R56, thereby reducing the on-resistance loss. As the discharge current decreases, the D-S voltage difference decreases. When the current approaches 0, the MOSFET tube Q9 and the MOSFET tube Q10 are turned off, and they wait to be turned on in the next cycle.

[0046] Referring to Figure 6, the light emitting device of the optocoupler and the common terminal of the voltage regulator are also connected with a compensation loop, the other terminal of the compensation loop is connected with a sampling circuit, the two terminals of the sampling circuit are connected between the positive and negative output terminals of the secondary side synchronous rectification module respectively, and the regulating terminal of the voltage regulator is connected with the compensation loop. Specifically, the other terminal of the sixty-fifth resistor R64 is connected with the common terminal of the light emitting device U3A of the optocoupler and the voltage regulator U5, and the other terminal of the thirtieth capacitor C30 is connected with the regulating terminal REF of the voltage regulator. The sampling circuit comprises the sixty-sixth resistor R66 and the sixty-seventh resistor R67 connected in series, the other terminal of the sixty-sixth resistor R66 is connected with the output terminal positive pole of the secondary side synchronous rectification module, the other terminal of the sixty-sixth resistor R66 is connected with the ground, and the common terminal of the sixty-sixth resistor R66 and the sixty-seventh resistor R67 is connected with the thirtieth capacitor C30 and the regulating terminal REF of the voltage regulator U5 respectively.

[0047] When the output voltage Vout of the secondary side synchronous rectification module becomes high, the REF pin (the regulating terminal of the voltage regulator U5) voltage of the voltage regulator U5 becomes high through the sampling circuit of the resistor R66, the resistor R67 and the resistor R68, the current flowing through the K-A terminal of the voltage regulator U5 increases, and the current flowing through the light emitting device U3A of the optocoupler U3 also increases, so that the voltage of the light receiving device U3B of the optocoupler U3 decreases, the voltage detected by the FB pin of the LCC module of the power supply driving chip U2 decreases, the power supply driving chip U2 correspondingly reduces the on time of the switch tube Q2 and the switch tube Q3 of the LLC module, so as to reduce the output voltage. Conversely, when the output voltage Vout becomes low, the REF pin voltage of the voltage regulator U5 becomes low, the current flowing through the K-A terminal of the voltage regulator U5 decreases, the current flowing through the light emitting device U3A of the optocoupler U3 also decreases, so that the voltage of the light receiving device U3B of the optocoupler U3 increases, the voltage of the FB pin of the power supply driving chip U2 increases, the power supply driving chip U2 increases the on time of the switch tube Q2 and the switch tube Q3 of the LLC module, and the output voltage increases accordingly. Through the feedback circuit, the output ripple is reduced, and the purpose of no frequency flash is achieved.

[0048] Referring to Figure 7 to Figure 10 , the light adjusting circuit framework of the DALI protocol is shown. Figure 7 The circuit principle diagram of the DALI module is shown, Figure 8 The circuit principle diagram of the power supply module is shown, Figure 9 The circuit principle diagram of the digital signal processor is shown, Figure 10 The circuit principle diagram of the constant voltage light adjusting control module is shown.

[0049] Referring to Figure 7 and Figure 9The digital signal processor comprises a digital signal processing chip U14, the DALI module comprises a surge suppression rectifier module, a digital signal processing module and an optical coupling isolation transmission module connected in sequence. The input end of the surge suppression rectifier module is connected with the D4i host, and the optical coupling isolation transmission module is connected with the digital signal processor. When the D4i host inputs a low-voltage digital signal, the switch tube Q7 and the switch tube Q12 are turned on, and the digital signal is fed back to the digital signal processing chip U14 through the light emitter U7A; when the D4i host inputs a high-voltage mains, the switch tube Q14 is turned on through rectification filtering and surge absorption, and the signal is fed back to the digital signal processing chip U14 through the light emitter U7A. When the digital signal processing chip U14 receives the digital signal fed back by the light receiver U7B, the PIN14 of the digital signal processing chip U14 sends a PWM dimming signal to the driving pin of the digital signal processing chip U14 to realize the adjustment of brightness change.

[0050] When the digital signal processing chip U14 sends a signal, the signal is fed back to the DALI module through the light receiver U6B, so that the switch tube Q5 and the switch tube Q6 are turned on, and the signal is transmitted back to the D4i host.

[0051] The digital signal processor further comprises a temperature sensing module connected with the digital signal processor, the temperature sensing module being close to the digital signal processor, for collecting the running temperature signal of the digital signal processor and transmitting the temperature signal to the digital signal processor.

[0052] Referring to Figure 8 The power supply module comprises a step-down converter U9 and a step-down chip U11. The step-down converter U9 adopts MP4562, the input end of the step-down converter U9 is connected with the output end VOUT+ of the secondary side synchronous rectification module, the output end of the step-down converter U9 is connected with the inductor L3, and the power supply VCC+ is output after RC filtering. The input end of the step-down chip U11 is connected with the power supply VCC+, and a 3.3V power supply is output. The step-down converter U9, the inductor L3 and the step-down chip U11 constitute a BUCK step-down circuit. When the built-in MOSFET of the chip MP4562 is turned on, the current flows through the inductor L3, and the current linearly increases before the inductor is saturated. The current flows through the load at the same time, and the capacitors C41 and C43 are charged. The digital signal processing chip U14 is provided with energy. When the built-in MOSFET is turned off, the inductor L3 is discharged through the freewheeling diode D25, the inductor L3 current linearly decreases, and the output voltage is maintained by the discharge of the capacitors C41 and C43 and the reduced inductor current.

[0053] Figure 10The constant-voltage dimming control module comprises two groups of voltage regulating components and MOSFET switch tubes connected to the output ends of the voltage regulating components; the control ends of the MOSFET switch tubes are connected to the output ends of the voltage regulating components, and the electrode ends of the MOSFET switch tubes are connected to the ground and the LED load respectively. Specifically, the voltage regulating components comprise voltage regulating chips U13 and U12, the MOSFET switch tubes comprise switch tubes Q21 and Q22, the control end of the switch tube Q21 is controlled by the output end of the voltage regulating chip U12, the control end of the switch tube Q22 is controlled by the output end of the voltage regulating chip U13, the source electrodes of the switch tubes Q21 and Q22 are connected to the ground, and the drain electrodes are connected to the LED load through diodes and common-mode inductors. The input ends of the voltage regulating chips U13 and U12 are connected to the digital signal processing chip U14, the voltage regulating chips U13 and U12 convert the 3.3V PWM signal provided by the digital signal processing chip U14 into a 5V PWM signal, the 5V PWM signal controls the opening and closing of the switch tubes Q21 and Q22, and thus the dimming of the LED is realized.

[0054] The constant-voltage dimming control module further comprises a short-circuit, open-circuit and overload protection detection circuit, which comprises an amplifier U10, comparators U15 and U16, first and second voltage dividing components.

[0055] The source electrode of the switch tube Q21 is connected to the amplifier U10 through a resistor R99, and a capacitor C50 is connected in parallel between the end of the resistor R99 close to the comparator U10 and the ground; the source electrode of the switch tube Q22 is connected to the amplifier U10 through a resistor R105, and a capacitor C51 is connected in parallel between the end of the resistor R105 close to the amplifier U10 and the ground. The two output ends of the amplifier are connected to the input ends of the comparators U15 and U16 respectively, and the output ends of the comparators U15 and U16 are connected to the digital signal processing chip U14. When the current generated by the short-circuit load is filtered and processed through the resistors R99 and R105, the capacitors C50 and C51 and the operational amplifier U10, a pulse signal greater than the reference voltage 0.7V of the comparators U15 and U16 is generated, the comparators U15 and U16 output high-level signals to the digital signal processing chip U14, and the short-circuit data is fed back to the D4i bus through the light-emitting device U6A of the optocoupler.

[0056] The first voltage division assembly is provided with two groups corresponding to the switch tube Q21 and the switch tube Q22, the first group includes the capacitor C56, the resistor R7, the resistor R85, the resistor R104 and the capacitor C53, and the second group includes the capacitor C57, the capacitor C54, the resistor R10, the resistor R106 and the resistor R86. The voltage generated when the load is overloaded is filtered through the resistor R99, the resistor R105, the capacitor C50 and the capacitor C51, is amplified through the operational amplifier U10, is divided through the first voltage division assembly, is sent to the digital signal processing chip U14, and the overload data is fed back to the D4i bus through the cooperation of the light emitting device U6A and the light receiving device U6B of the optocoupler U6.

[0057] The second voltage division assembly is provided with two groups corresponding to the switch tube Q21 and the switch tube Q22, the first group includes the resistor R59, the capacitor C31, the capacitor C33, the resistor R124 and the diode D23 connected to the drain of the switch tube Q21, and the second group includes the resistor R83, the resistor R125, the capacitor C32, the capacitor C44 and the diode D24 connected to the drain of the switch tube Q22. When the load is opened, the drain voltage of the switch tube Q21 and the switch tube Q22 is divided through the second voltage division assembly and is sent to the digital signal processing chip U14, and the overload data is fed back to the D4i bus through the cooperation of the light emitting device U6A and the light receiving device U6B of the optocoupler U6.

[0058] The above description shows and describes the preferred embodiments of the utility model, and it should be understood that the utility model is not limited to the forms disclosed herein, and should not be considered as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be modified within the scope of the utility model concept disclosed herein through the above teaching or related technical or knowledge. The modification and change made by the person skilled in the art without departing from the spirit and scope of the utility model should be within the protection scope of the utility model claims attached herein.

Claims

1. A constant voltage LED driving circuit, characterized by, Comprise: MCU; Filter rectifier module for accessing alternating current and converting to direct current; PFC module connected with the output end of the filter rectifier module, the filter rectifier module is used for power supply for the PFC module, the PFC module is used for power factor correction; LLC module connected with the PFC module and MCU, the PFC module is used for power supply for the LLC module, and MCU controls the LLC module to be used for further converting the direct current output by the PFC module into direct current voltage of the size required by the load; Secondary side synchronous rectification module connected with the output end of the LLC module, used for output rectification of the output power of the LLC module, thereby supplying to the load LED; Optocoupler isolation feedback module connected with the output end of the secondary side synchronous rectification module and the LLC module, used for sampling the output voltage of the secondary side synchronous rectification module and feeding back to MCU.

2. The constant voltage LED driving circuit according to claim 1, wherein Also comprise: DALI module connected with D4i host, used for accepting and transmitting the signal sent by the D4i host; Digital signal processor connected with the DALI module, used for receiving and processing the dimming signal sent by the DALI module; Constant voltage dimming control module connected between the output end of the secondary side synchronous rectification module and the load LED, the constant voltage dimming control module is also connected with the digital signal processor, used for dimming the load LED according to the dimming signal; Power supply module connected with the output end of the secondary side synchronous rectification module, the power supply module is also connected with the digital signal processor and the constant voltage dimming control module, used for power supply for the digital signal processor and the constant voltage dimming control module.

3. The constant voltage LED driving circuit according to claim 2, wherein Also include temperature sensing module connected with the digital signal processor, the temperature sensing module is close to the digital signal processor, used for collecting the running temperature signal of the digital signal processor and transmitting the temperature signal to the digital signal processor.

4. The constant voltage LED driving circuit according to claim 2, wherein The DALI module comprises sequentially connected surge suppression rectifier module, digital signal processing module and optocoupler isolation transmission module; the input end of the surge suppression rectifier module is connected with the D4i host, and the optocoupler isolation transmission module is connected with the digital signal processor.

5. The constant voltage LED driving circuit according to claim 2, wherein The constant voltage dimming control module comprises a voltage regulating assembly and a MOSFET switch tube connected with the output end of the voltage regulating assembly; the control end of the MOSFET switch tube is connected with the output end of the voltage regulating assembly, and the electrode end of the MOSFET switch tube is connected with the ground and the load LED respectively.

6. A constant voltage LED driving circuit according to claim 5, wherein Also include protection module arranged between the digital signal processor and the constant voltage dimming control module, the protection module comprises an amplifier, a comparator, a first voltage dividing assembly and a second voltage dividing assembly; The amplifier is connected with the constant voltage dimming control module, the output end of the amplifier is connected with the comparator, and the output end of the comparator is connected with the digital signal processor; The first voltage dividing assembly is connected between the output end of the amplifier and the digital signal processor; and the second voltage dividing assembly is connected between the constant voltage dimming control module and the digital signal processor.

7. The constant voltage LED driving circuit according to claim 1, wherein The LLC module comprises a resonant inductor, a transformer primary winding and a resonant capacitor which form a loop with the output end of the filter rectifier module, a second switch tube with two electrode ends connected in series between the output end of the filter rectifier module and the resonant inductor, and a third switch tube with two electrode ends connected in parallel at two ends of the resonant inductor and the resonant capacitor away from each other, and the control ends of the second switch tube and the third switch tube are connected with the MCU.

8. The constant voltage LED driving circuit according to claim 2, wherein, The secondary side synchronous rectification module comprises a synchronous rectification chip, a rectification bridge and a filter capacitor group, the synchronous rectification chip is connected with the power supply module, the filter capacitor group is connected in parallel between the output end of the secondary side synchronous rectification module and the ground, and the rectification bridge is composed of at least four field effect tubes.

9. The constant voltage LED driving circuit according to claim 1, wherein, The optocoupler isolation feedback module comprises a sixth ninth resistor connected in series, a light emitting device of an optocoupler and a voltage stabilizer, the other end of the sixth ninth resistor is connected with a power supply, the other end of the voltage stabilizer is connected with the ground, and the light receiving device of the optocoupler is connected with the MCU. The common end of the light emitting device of the optocoupler and the voltage stabilizer is further connected with a compensation loop, the other end of the compensation loop is connected with a sampling circuit, the two ends of the sampling circuit are respectively connected between the positive and negative poles of the output end of the secondary side synchronous rectification module, and the adjusting end of the voltage stabilizer is connected with the compensation loop.

10. The constant voltage LED driving circuit according to claim 9, wherein, The compensation loop comprises a sixth fifth resistor and a thirtieth capacitor connected in series, the other end of the sixth fifth resistor is connected with the common end of the light emitting device of the optocoupler and the voltage stabilizer, and the other end of the thirtieth capacitor is connected with the adjusting end of the voltage stabilizer. The sampling circuit comprises a sixth sixth resistor and a sixth seventh resistor connected in series, the other end of the sixth sixth resistor is connected with the positive pole of the output end of the secondary side synchronous rectification module, the other end of the sixth sixth resistor is connected with the ground, and the common end of the sixth sixth resistor and the sixth seventh resistor is respectively connected with the thirtieth capacitor and the adjusting end of the voltage stabilizer.

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