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LED drive power EMI rectification program

From: Data:08/08/2016


LED driving power supply EMI rectification scheme 2012-4-30 21:36 1MHz ---- to differential mode interference based 1. Increase of X electric capacity; 2. Adding differential mode inductors; 3. The small power power source can use PI type filter processing (near the transformer of the electrolytic capacitor can choose some of the larger). 1MHZ---5MHZ--- differential mode and common mode by a combination of input are connected in parallel with a series of X capacitor to filter out bad touch interference and the analysis is what kind of interference and exceeded to solve. For differential mode interference exceeded can adjust x electric capacity, adding differential mode inductors, adjustment mode inductance; 2. For the common mode interference exceeds the standard, the common mode inductance can be added, choose reasonable inductance to suppress; 3. Can also change the rectifying diode characteristics to deal with a pair of fast diodes such as FR107 a pair of ordinary 1N4007 rectifier diode. 5M--10M--- is mainly used to touch the interference, using the method of restraining the common touch. For the shell of the earth, in line with a ring on around 2-3 times of more than 10MHz interference have larger attenuation; can choose close to the transformer iron core stick copper foil, copper foil closed-loop. Rear output rectifier tube absorption circuit and primary circuit parallel capacitor size. 20--30MHZ, 1. For a class of products can be by adjusting the Y2 capacitors or change Y2 capacitors position; 2. Adjustment of a secondary side of Y1 capacitor locations and parameters of value; 3. In transformer bread copper foil; transformer in the layer shielding layer; adjustment of the transformer windings arrangement. 4. Change the PCB layout; 5. Output line in front after a two-wire and around small common mode inductors; 6. In the rectifier output pipe connected in parallel at both ends of the RC filter and a reasonable adjustment parameters; 7. In between the transformer and MOSFET with bead core; 8. At the foot of the transformer input voltage and a small capacitor. Constitute a small heart; 8.PCB between the parallel connected in series with or to solve slow with the voltage of power supply by buffer; 2.RCD cause is generally.30---50MHZ---. With increasing MOS driver resistance MOS tube high-speed turn-on and turn off 1. With increasing MOS driver resistance circuit 1N4007 slow; 3.VCC 1N4007 tube. The output lines on the front of a bifilar wound small common mode inductors. The MOSFET D-S feet a small absorption circuit. In the transformer and MOSFET with bead core. In the transformer input voltage pin and a small capacitor layout electrolytic capacitor, transformer, MOS circuit ring as much as possible. Transformer, the output diode, the output smoothing electrolytic capacitor circuit ring as much as possible. 50---100MHZ--- is generally output rectifier reverse recovery current caused by 1. In the rectifier tube string beads; 2. Adjust the output rectifier tube of snubber circuit parameters; 3. Can change the secondary side is connected across the Y capacitor branch impedance, such as pin with the bead core or on the appropriate resistor; 4. Can also be change the MOSFET, output rectifier diode ontology to the space radiation (such as iron clamp MOSFET; iron clamp diode, radiator changes take place). 5 increase in copper foil shield.200MHZ---300MHZ--- switching power supply to the space radiation suppression has been basically the amount of radiation is very small, generally over EMI standard supplement: high frequency switching power transformer is generally between the first shielding layer, without hanging. The above is a high-frequency switching power supply products, PCB yuan EMI. on the layout of the device, please pay close attention to this point. If there is a mechanical switching power supply shell, shell structure has a great influence on radiation. Please pay close attention to this point. The main switch manufacturers, different parameters of the main diode have some differences, have a certain impact on the EMC. Please pay close attention to this.

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