The LED power supply made by the constant current type control IC represented by the 9910 series is actually current limiting, and the control is relatively simple. Strictly speaking, it is not the mainstream mode of switching power supply control. The mainstream mode of switching power supply control must be Benchmarks and op amps. But this kind of IC can only be used for LEDs, it is difficult to use for other things, just because LEDs have extremely low ripple requirements. But because it is only used for LEDs, it is now more expensive. Basically, it is made by using 9910 plus MOS tube, and the output is electroless. Generally, I think many people use the word inductor to do the power conversion inductor. This kind of power supply, the general manufacturer's chip data has a picture, basically all of them are buck. I don't say much, and there are more people who are better than me.
The second is based on me, that is, the constant current driver of the switching power supply control mode. This is the common switching power supply chip as the core conversion device, such a lot of chips, such as PI's TNY series, TOP series, ST's VIPER12, VIPER22, Fairchild's FSD200, etc., even using only triode or MOS tube RCC, etc., can be done. The benefits are low cost and good reliability. Because the ordinary switching power supply chip is not only good price, but also a classic product that has been used extensively. Such an IC is generally integrated with a MOS tube, which is more convenient than the 9910 plus MOS, but the control method is more complicated, and it is necessary to add a constant current control device, and a triode or an operational amplifier can be used. Magnetic components can be used with I-shaped inductors or high-frequency transformers with air gaps.
I love to use a transformer, because the cost of the inductor is very low, but I don't think it has the ability to load, and the adjustment is not flexible. Therefore, I think the better device choice is that the common integrated MOS switching power supply chip plus high-frequency transformer is the most ideal choice in terms of performance and cost. It does not need to use any constant current IC, that kind of thing, Not easy to use, expensive.
Finally, to distinguish between the two power supplies, one of the most important methods is to see if the output has electrolytic capacitors for filtering.
Regarding the power supply problem, whether it is a power supply with current limiting constant current control or a constant current power supply controlled by an operational amplifier, the power supply problem must be solved. That is, when the switching power supply chip works, it needs a relatively stable DC voltage to supply power to its chip. The working current of the chip varies from one MA to several MAs. There is a kind of FSD200, NCP1012, and HV9910. This kind of chip is high-voltage self-feeding. It is convenient to use, but high-voltage feeding causes the IC heat to rise because the IC has to withstand about 300V DC, as long as it has a little current. Even if it is an MA, it has zero damage of zero watts. Generally, the LED power supply is only about ten watts. If you lose a few watts, you can pull down the efficiency of the power supply by a few points. There is also a typical like QX9910. Use the resistor to pull down the power, so that the loss is on the resistor, and it will lose about a few watts. There is also magnetic coupling, which is to use a transformer to add a winding to the main power coil, just like the auxiliary winding of the flyback power supply, so as to avoid losing the power of a few watts. This is one of the reasons why I don't isolate the power supply and use the transformer. In order to avoid losing the power of a few watts, I will increase the efficiency by a few points.
Non-isolated buck power supply design method Non-isolated buck type is a commonly used power supply structure, which accounts for almost 90% of the fluorescent lamp power supply. Many people think that there is only one type of step-down type that does not isolate the power supply. When it comes to isolation, it is thought to be a step-down type. It is thought that the lamp is not safe - after the power supply is damaged. In fact, the buck type is only one kind, there are two basic structures, namely boost, and buck-boost, ie BOOSTANDBUCK-BOOST, even if the latter two power supplies are damaged. It does not affect the LED and has this benefit.
Now LED fluorescent lamp power supply, manufacturers of lamps are generally required to be placed in the lamp, such as in the T8 lamp. Very few are external. I don't know why this is the case. In fact, the built-in power supply is difficult to do, and the performance is not good. But I don't know why there are so many people asking for it. It may be down with the wind. The external power supply should be said to be more scientific and more convenient. But I also have to fall with the wind, what the customer wants, I will do. But doing the built-in power supply is quite difficult. Because the external power supply, the shape is basically not required, how much you want to do, and what shape you want to make does not matter. The built-in power supply can only be made into two types, one of which is the most used, that is, placed under the light board and placed on the light board.
The following is the power supply, so the power supply is required to be very thin, otherwise it will not fit. Moreover, the component can only be dropped, and the line on the power supply is only lengthened. I don't think this is a good idea. However, everyone generally likes to do this. I will do it. There is also less use, put the two ends, that is, placed on both ends of the lamp, so that it is better to do, the cost is lower. I have also done it, basically the two built-in shapes.
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