Anti-electromagnetic interference non-isolated LED driving power supply

Abstract

The invention discloses an anti-electromagnetic interference non-isolated LED driving power supply, which comprises an LED driving circuit, the LED driving circuit comprises an EMI filter, a power supply, a Boost PFC circuit, a Buck circuit and a resistor R0, one side of the power supply is connected in parallel with one side of the EMI filter, the other side of the EMI filter is connected in parallel with one end of the Boost PFC circuit, and the other end of the Boost PFC circuit is connected in parallel with one end of the Buck circuit. The switching tube and the power inductor can be regarded as main common-mode noise sources; the number of the main common-mode transmission paths is two, the first common-mode transmission path is a loop formed by a distributed capacitor between the switch tube and the radiator, a distributed capacitor between the radiator and the ground, the ground, the LISN and the L / N line, and the second common-mode transmission path is a loop formed by a distributed capacitor between the outermost winding of the power inductor and the ground, the ground, the LISN and the L / N line. The main common-mode noise source of the prototype is judged to be a post-stage Buck circuit by combining an experimental result without a filter when the prototype is fully loaded and theoretical analysis.

Description

Technical Field

[0001] The present invention relates to the technical field of LED driver power supplies, and in particular to a non-isolated LED driver power supply that is resistant to electromagnetic interference. Background Art

[0002] With the advancement of technology, the LED lighting industry has experienced significant growth. LED drivers are key components of LED lighting systems and a prerequisite for their safe and stable operation. While LED driver technology has matured in recent years, high reliability, high efficiency, and high power density remain the key development trends. The Boost+Buck circuit topology is widely used in medium- and high-power LED drivers due to its simple structure and excellent constant current performance.

[0003] Power electronic power converters are widely used in the field of LED driver power supplies due to their unique advantages such as high efficiency and small size. When the power semiconductor devices of LED driver power supplies operate in a high-frequency switching state, they will generate a very high rate of change of voltage and current, which will cause serious electromagnetic interference problems through parasitic inductance and capacitance in the circuit. This will not only pollute the power grid environment, but also interfere with the normal operation of other equipment in the same power grid, and may also cause potential harm to human health. In particular, with the continuous increase in the switching frequency of power semiconductor devices, the power density of LED driver power supplies will be further improved, and the generation and transmission mechanism of electromagnetic interference will become more complex. For LED driver power supplies, electromagnetic compatibility performance analysis and design are the main technical means to ensure that the electromagnetic interference generated by them complies with the relevant electromagnetic compatibility standards. The difficulty of electromagnetic compatibility performance analysis and design is also becoming more and more difficult. Electromagnetic compatibility characteristics are important performance indicators of LED driver power supplies. In order to enable electrical and electronic equipment to have sufficient anti-interference ability in the electromagnetic environment in which they are located, and to prevent the electromagnetic interference generated by them from affecting the normal operation of other equipment.

[0004] At present, EMI filters are still the main technical approach to optimize the conducted EMI of power converters. They are divided into three types: passive, active and hybrid. Among them, passive filters are the most widely used due to their simple principles, easy design and low cost. The meaning of electromagnetic compatibility can be summarized as: the ability of electrical equipment to ensure its normal operation in the electromagnetic interference environment and not cause unbearable electromagnetic interference to other equipment in the environment. Therefore, EMC research can be divided into two directions: electromagnetic susceptibility and electromagnetic interference. Among them, EMI can be further divided into two aspects: conducted interference and radiated interference; EMS can be further divided into two aspects: conducted susceptibility and radiated susceptibility.

[0005] However, traditional LED driver power supplies have the following disadvantages:

[0006] When conducting electromagnetic compatibility performance design for LED driver power supplies, EMI experimental testing is often carried out on the basis that the engineering prototype meets the basic performance indicators such as efficiency, power and stability. When the product does not meet the requirements of the relevant electromagnetic compatibility standards, engineers usually rely on their own product design experience and adopt a trial-and-error method to make corrections or even redesign, which greatly affects the development cycle and design cost of the LED driver power supply. Summary of the Invention

[0007] The purpose of the present invention is to provide a non-isolated LED driver power supply that is resistant to electromagnetic interference, so as to solve the problem raised in the above background technology that when conducting electromagnetic compatibility performance design for LED driver power supplies, EMI experimental testing is often carried out on the basis that the engineering prototype meets the basic performance indicators such as efficiency, power and stability. When the product does not meet the requirements of the relevant electromagnetic compatibility standards, the engineering personnel usually rely on their own product design experience to adopt a trial-and-error method to make corrections or even redesign, which greatly affects the development cycle and design cost of the LED driver power supply.

[0008] To achieve the above object, the present invention provides the following technical solution: an electromagnetic interference resistant non-isolated LED driver power supply, comprising an LED driver circuit, wherein the LED driver circuit comprises an EMI filter, a power supply, a Boost PFC circuit, a Buck circuit, and a resistor R0, wherein one side of the power supply is connected in parallel with one side of the EMI filter, the other side of the EMI filter is connected in parallel with one end of the Boost PFC circuit, the other end of the Boost PFC circuit is connected in parallel with one end of the Buck circuit, and the other end of the Buck circuit is connected in parallel with both ends of the resistor R0.

[0009] As a preferred technical solution of the present invention, the Boost PFC circuit includes a diode D2, a diode D3, a Boost power inductor L3, a freewheeling diode D1, an output filter capacitor C out , switch tube T1, input filter capacitor C inp , diode D4 and diode D5, one end of the diode D2 is connected to one end of the diode D3, the other end of the diode D3 is connected to one end of the diode D5, the other end of the diode D5 is connected to one end of the diode D4, and the two ends between the diode D3 and the diode D5 are connected to the input filter capacitor C inp In parallel, the diode D3 and the input filter capacitor C inp The connection of is connected to one end of the Boost power inductor L3, and the other end of the Boost power inductor L3 is connected to one end of the switch tube T1 and one end of the freewheeling diode D1 respectively. The diode D5 is connected to the input filter capacitor C inpThe connection point is connected to the other end of the switch tube T1, and the freewheeling diode D1 and the switch tube T1 are connected to the output filter capacitor C out in parallel.

[0010] As a preferred technical solution of the present invention, the other end of the diode D2 and the other end of the diode D4 are both connected to the EMI filter, and the output filter capacitor C out Both ends of the MOSFET are connected to the Buck circuit.

[0011] As a preferred technical solution of the present invention, the Buck circuit includes a switch tube Q1, a Buck power inductor L, a freewheeling diode VD1 and an output filter capacitor C o One end of the switch tube Q1 is connected to one end of the Buck power inductor L and one end of the freewheeling diode VD1 respectively, and the other end of the Buck power inductor L and the other end of the freewheeling diode VD1 are connected to the output filter capacitor C o Connect both ends of .

[0012] As a preferred technical solution of the present invention, one side of the switch tube Q1 and one side of the freewheeling diode VD1 are both connected to the Boost PFC circuit, and the output filter capacitor C o Both sides are connected to the output load R o connect.

[0013] Compared with the prior art, the present invention has the following beneficial effects:

[0014] 1. Non-isolated LED driver power supply circuit structure. The conducted common-mode EMI noise mechanism of the experimental prototype based on a typical Boost PFC+Buck circuit is analyzed, including the conducted common-mode EMI noise source, noise transmission path, and electromagnetic interference noise equivalent model. Secondly, the main common-mode noise source of the prototype is identified as the subsequent Buck circuit. Finally, from the perspective of constructing an anti-phase noise voltage source, an active suppression method for the Buck circuit common-mode EMI noise is proposed by adding an anti-phase winding to the power inductor. The correctness and effectiveness of the proposed method are verified through conducted EMI test experiments.

[0015] 2. For boost and buck circuits, the switching transistor and power inductor can be considered the main common-mode noise sources. There are two main common-mode transmission paths: the first is a loop formed by the distributed capacitance between the switching transistor and the heat sink, the distributed capacitance between the heat sink and the ground, the ground, the LISN, and the L / N line. The second is a loop formed by the distributed capacitance between the outermost winding of the power inductor and the ground, the ground, the LISN, and the L / N line.

[0016] 3. By combining the experimental results and theoretical analysis of the prototype without a filter at full load, it is determined that the main common-mode noise source of the prototype is the post-stage Buck circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A circuit diagram of the present invention;

[0018] Figure 2 This is a diagram of the common-mode EMI noise transmission path of the Boost PFC circuit of the present invention;

[0019] Figure 3 This is a diagram showing an equivalent model of the common-mode EMI noise conducted by the Boost PFC circuit of the present invention;

[0020] Figure 4 This is a diagram of the common-mode EMI noise transmission path conducted by the Buck circuit of the present invention;

[0021] Figure 5 This is the equivalent model diagram of the Buck circuit conducted common-mode EMI noise of the present invention;

[0022] Figure 6 This is a physical picture of the Boost PFC+Buck topology prototype of the present invention;

[0023] Figure 7 This is the original common-mode noise spectrum of the Boost PFC+Buck circuit under full load conditions of the present invention;

[0024] Figure 8 This is the insertion loss curve of the Buck circuit reverse winding method of the present invention. DETAILED DESCRIPTION

[0025] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0026] See also Figure 1-8 The present invention provides a non-isolated LED driver power supply with electromagnetic interference resistance, including an LED driver circuit, which includes an EMI filter, a power supply, a Boost PFC circuit, a Buck circuit, and a resistor R0. One side of the power supply is connected in parallel with one side of the EMI filter, the other side of the EMI filter is connected in parallel with one end of the Boost PFC circuit, the other end of the Boost PFC circuit is connected in parallel with one end of the Buck circuit, and the other end of the Buck circuit is connected in parallel with both ends of the resistor R0.

[0027] The Boost PFC circuit includes diode D2, diode D3, Boost power inductor L3, freewheeling diode D1, and output filter capacitor C out , switch tube T1, input filter capacitor C inp , diode D4 and diode D5, one end of diode D2 is connected to one end of diode D3, the other end of diode D3 is connected to one end of diode D5, the other end of diode D5 is connected to one end of diode D4, and the two ends between diode D3 and diode D5 are connected to the input filter capacitor C inp In parallel, diode D3 and input filter capacitor C inp The connection of is connected to one end of the Boost power inductor L3, and the other end of the Boost power inductor L3 is connected to one end of the switch tube T1 and one end of the freewheeling diode D1 respectively. The diode D5 is connected to the input filter capacitor C inp The connection point is connected to the other end of the switch tube T1, and the freewheeling diode D1 is connected to the switch tube T1 and the output filter capacitor C out in parallel.

[0028] The other end of diode D2 and the other end of diode D4 are connected to the EMI filter, and the output filter capacitor C out Both ends of the MOSFET are connected to the Buck circuit.

[0029] The Buck circuit includes the switch tube Q1, Buck power inductor L, freewheeling diode VD1 and output filter capacitor C o One end of the switch tube Q1 is connected to one end of the Buck power inductor L and one end of the freewheeling diode VD1 respectively, and the other end of the Buck power inductor L and the other end of the freewheeling diode VD1 are connected to the output filter capacitor C o Connect both ends of .

[0030] One side of the switch tube Q1 and one side of the freewheeling diode VD1 are connected to the Boost PFC circuit, and the output filter capacitor C o Both sides are connected to the output load R o connect.

[0031] In the present invention, in conjunction with the appended Figure 1 ,In the front-stage BoostPFC circuit, diodes D2-D5 form an input rectifier bridge;

[0032] In conjunction with the instructions Figure 2 , the conducted common-mode EMI noise transmission path of the Boost PFC circuit, where the inductors L1, L2, and resistors R1, R2 form the LISN, L1 = L2 = 50μH, C1 = C2 = 1μF, C3 = C4 = 0.1μF, R1 = R2 = 50Ω; C inpis the input filter capacitor; L3 is the Boost power inductor; D1 is the freewheeling diode; T1 is the switch tube; C out is the output filter capacitor; R out is the output load; C le is the power inductor, the distributed capacitance between the outermost winding of L3 and the ground or the casing; C th is the distributed capacitance between the switch tube T1 and the radiator; C he is the distributed capacitance between the radiator and the ground;

[0033] The rapid on-off switching of switch T1 generates a very high voltage change rate, or dv / dt. This in turn generates abundant high-order harmonics in the LED driver circuit, creating serious EMI problems. Furthermore, the voltage jump caused by the switch operation is also reflected in the magnetic component, power inductor L3. The potential at point P also jumps with the operation of switch T1. Therefore, in the analysis of conducted common-mode EMI noise mechanisms, the switch and power inductor can be considered the primary common-mode noise sources, and point P is the primary potential jump point in the Boost PFC circuit.

[0034] In conjunction with the instructions Figure 3 , R CM is the equivalent common-mode resistance at the LISN end, R CM =25Ω; ​​uP is the common mode noise voltage source. In the common mode EMI noise equivalent model, the common mode noise current i CM1 、i CM2 At μA level, the equivalent common-mode resistance R CM The voltage drop across the MOSFET is much smaller than the common-mode noise voltage source uP, so i CM1 、i CM2 Expressed as:

[0035]

[0036] C th 、C he The size of C mainly depends on the relative cross-sectional area and relative position between the switch tube T1 and the radiator, the radiator and the ground or the casing. le The size of is mainly determined by the relative cross-sectional area and relative position between the outermost winding of the power inductor L3 and the ground;

[0037] In conjunction with the instructions Figure 4 The switch tube Q1 and the power inductor L are the main common-mode noise sources of the Buck circuit. Point A is the main potential jump point in the Buck circuit. There are two main transmission paths for the conducted common-mode EMI noise of the Buck circuit: the first path passes through the potential jump point A and the distributed capacitance C between the switch tube Q1 and the heat sink. ms , the distributed capacitance C between the radiator and the earth casingsg The ground, LISN, and L / N lines form a loop, and the common-mode current flowing through this common-mode EMI noise transmission path corresponds to i in the figure. cm1 The second path passes through the distributed capacitance C between the outermost winding of the magnetic component power inductor L and the ground. lg , earth, LISN, and L / N lines form a loop. The common-mode current flowing through this common-mode EMI noise transmission path corresponds to i in the figure. cm2 ;

[0038] In conjunction with the instructions Figure 5 , common mode noise current i cm1 、i cm2 Small, at the microampere level, the voltage drop on the equivalent common-mode resistor RCM is much smaller than the common-mode noise voltage source uA, so i cm1 、i cm2 Expressed as:

[0039]

[0040] Capacitor C ms , capacitor C sg The size of the capacitor C mainly depends on the relative cross-sectional area and relative position between the switch tube Q1 and the radiator, and the radiator and the ground. lg The size of is mainly determined by the relative cross-sectional area and relative position between the outermost winding of the power inductor L and the ground;

[0041] In conjunction with the instructions Figure 6 In the optimization of conducted EMI characteristics, in order to propose targeted EMI characteristics optimization strategies, identifying the original noise spectrum of the prototype is the key foundation. According to the provisions of the CISPR22 standard, the EMI test platform is laid out. The current method is used to separate differential and common mode noise. The EMI receiver, LISN, and current clamp used are KH3939, KH3763, and KH23101 from Kehuan Century respectively.

[0042] In conjunction with the instructions Figure 7, First, from the original common-mode noise spectrum, it can be seen that there are obvious noise peak points in the frequency bands of 50 kHz - 58 kHz, 100 kHz - 116 kHz, 150 kHz - 174 kHz, 200 kHz - 232 kHz, 250 kHz - 290 kHz, 300 kHz - 348 kHz, 350 kHz - 406 kHz, etc. This coincides with the frequency doubling of the switching frequency of the Buck circuit. Therefore, it is initially judged that the subsequent Buck circuit is the main common-mode noise source of this prototype. Secondly, from the theoretical analysis, the switching frequencies of the pre-stage Boost circuit are relatively dispersed, while the switching frequencies of the subsequent Buck circuit are relatively concentrated. Therefore, the proportion of common-mode noise of the Buck circuit should theoretically be larger than that of the Boost circuit. Combining the above experimental results and theoretical analysis, it is determined that the main common-mode noise source of the prototype is the subsequent Buck circuit;

[0043] Combined with the attached drawings of the specification Figure 8 , given the parameters of the reverse winding, within the conduction frequency band of 9 kHz - 30 MHz, it basically coincides with the insertion loss curve, with only a certain difference at the frequency point f3; when f < f2, the insertion loss is less than 0 dB, indicating that the reverse winding method can optimize the common-mode EMI characteristics of the Buck circuit within this frequency band. Especially when the frequency is f1, the common-mode noise suppression effect is the best; when f2 > f, the insertion loss is greater than 0 dB, indicating that the reverse winding method will deteriorate the common-mode noise.

[0044] Although the present invention has been described in detail with reference to the foregoing embodiments, for those skilled in the art, they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A non-isolated LED driver power supply with electromagnetic interference resistance, comprising an LED driver circuit, characterized in that: The LED driving circuit includes an EMI filter, a power supply, a Boost PFC circuit, a Buck circuit and a resistor R0. One side of the power supply is connected in parallel with one side of the EMI filter, the other side of the EMI filter is connected in parallel with one end of the Boost PFC circuit, the other end of the Boost PFC circuit is connected in parallel with one end of the Buck circuit, and the other end of the Buck circuit is connected in parallel with both ends of the resistor R0.

2. The electromagnetic interference resistant non-isolated LED driver power supply according to claim 1, characterized in that: The Boost PFC circuit includes a diode D2, a diode D3, a Boost power inductor L3, a freewheeling diode D1, an output filter capacitor C out , switch tube T1, input filter capacitor C inp , diode D4 and diode D5, one end of the diode D2 is connected to one end of the diode D3, the other end of the diode D3 is connected to one end of the diode D5, and the other end of the diode D5 is connected to one end of the diode D4.

3. The electromagnetic interference resistant non-isolated LED driver power supply according to claim 2, characterized in that: The two ends between the diode D3 and the diode D5 are connected to the input filter capacitor C inp In parallel, the diode D3 and the input filter capacitor C inp The connection point is connected to one end of the Boost power inductor L3, and the other end of the Boost power inductor L3 is connected to one end of the switch tube T1 and one end of the freewheeling diode D1 respectively.

4. The electromagnetic interference resistant non-isolated LED driver power supply according to claim 3, characterized in that: The diode D5 and the input filter capacitor C inp The connection point is connected to the other end of the switch tube T1, and the freewheeling diode D1 and the switch tube T1 are connected to the output filter capacitor C out in parallel.

5. The electromagnetic interference resistant non-isolated LED driver power supply according to claim 4, characterized in that: The other end of the diode D2 and the other end of the diode D4 are both connected to the EMI filter. The output filter capacitor C out The two ends of the circuit are connected to the BuCk circuit.

6. The electromagnetic interference resistant non-isolated LED driver power supply according to claim 1, characterized in that: The Buck circuit includes a switch tube Q1, a Buck power inductor L, a freewheeling diode VD1 and an output filter capacitor C o One end of the switch tube Q1 is connected to one end of L and one end of the freewheeling diode VD1 respectively, and the other end of the Buck power inductor L and the other end of the freewheeling diode VD1 are connected to the output filter capacitor C o Connect both ends.

7. The electromagnetic interference resistant non-isolated LED driver power supply according to claim 6, characterized in that: One side of the switch tube Q1 and one side of the freewheeling diode VD1 are both connected to the Boost PFC circuit, and the output filter capacitor C o Both sides are connected to the output load R o connect.

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