LED fluorescent power to a certain extent will cause burnout. On this issue, people have also seen posted discussions in industry forums. This article will discuss the LED fluorescent lamp power supply heat burnout MOS tube technology from chip heating, power tube heating, frequency reduction, inductor or transformer selection, LED current size and other aspects. 1, chip fever This content mainly focuses on the high-voltage driver chip with a built-in power modulator. If the current consumed by the chip is 2mA, the voltage of 300V is applied to the chip. The power consumption of the chip is 0.6W, which of course will cause the chip to heat up. The maximum current of the driver chip comes from the consumption of the driving power MOS transistor. The simple calculation formula is I=cvf (taking into account the charging resistor efficiency, the actual I=2cvf, where c is the cgs capacitor of the power MOS transistor, and v is the power transistor conduction When the gate voltage, so in order to reduce the chip's power consumption, must find ways to reduce c, v and f. If c, v and f can not be changed, then think of ways to split the chip's power consumption to off-chip devices, pay attention not to Introduce extra power consumption.The simpler one is to consider better heat dissipation. 2, power tube heating Power tube power consumption is divided into two parts, switching loss and conduction loss. It should be noted that in most applications, especially LED mains-driven applications, switching damage is much greater than conduction losses. Switching losses are related to the power supply's cgd and cgs, as well as the chip's driving ability and operating frequency. Therefore, to solve the power transistor heating can be resolved from the following aspects: a, can not be based on the size of the on-resistance to select the MOS power transistor, because the smaller the internal resistance, the greater the cgs and cgd capacitance. Such as 1N60's cgs is about 250pF, 2N60's cgs is about 350pF, 5N60's cgs is about 1200pF, the difference is too big, when choosing the power tube, enough to use on it. b, the rest is the frequency and chip driver capability, here only talk about the impact of frequency. The frequency and the conduction loss are also proportional to each other. Therefore, when the power tube is heated, it is first necessary to consider whether the frequency selection is a bit high. Try to reduce the frequency! However, it should be noted that when the frequency is reduced, in order to obtain the same load capacity, the peak current must increase or the inductance also becomes larger, which may cause the inductor to enter the saturation region. If the inductor saturation current is large enough, consider changing the CCM (Continuous Current Mode) to DCM (Discontinuous Current Mode), which requires a load capacitor. 3, operating frequency down This is also a common phenomenon in the debugging process. The down-clocking is mainly caused by two aspects. The ratio of input voltage and load voltage is small and system interference is large. For the former, be careful not to set the load voltage too high, although the load voltage is high, the efficiency will be high. For the latter, you can try the following aspects: a. Set the minimum current to a smaller point; b, clean wiring, especially the key path of the sense; c. Select a small point of inductance or choose the inductance of a closed magnetic circuit; d, plus RC low-pass filter it, this effect is a bit bad, C's consistency is not good, the deviation is a bit big, but for the lighting should be enough. In any case, there is no advantage in lowering the frequency, only the disadvantages, so it must be resolved. 4, the choice of inductance or transformer Finally I talked about the key points. I haven't started yet. I can only talk about the effects of saturation. Many users react, the same drive circuit, no problem with the inductance produced by a, and the inductor current produced with b becomes smaller. In this case, look at the inductor current waveform. Some engineers did not notice this phenomenon and directly adjusted the sense resistor or the working frequency to reach the required current. This may seriously affect the service life of the LED. So, before the design, a reasonable calculation is necessary. If the parameters of the theoretical calculation and the debugging parameters are a little different, it is necessary to consider whether the frequency reduction and transformer saturation. When the transformer is saturated, L will become smaller, resulting in a sharp increase in the peak current increase caused by the transmission delay, and then the LED peak current will increase. With the average current constant, you can only see the light decay. Gabion & Reno mattress is
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Features of Gabion & Reno mattress
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Durability
Gabions & Reno mattresses built from
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in ASTM A975-97.