How to make LED tube light power
Personally think that it is often practice forest for the trees only. Now before I ask about LED tube relative to the traditional lighting of the advantages which, first, energy saving, the second longevity, and is not afraid to switch, right. But now the use of high-PF method, are filled with passive valley PF circuit from the original drive, or 48 strings, 6 and instead, 12 and 24 strings, so, in the case of 220V, lower efficiency five percentage points or so, so] LED fluorescent lamp power supply , higher heat, light beads will also be some impact.
Another problem is that 24 string 12 and the practice, LED fluorescent lamp beads will become very hard to accept wiring, bad layout of the. I think the best way to string a bunch of 48 or a good way, mostly high efficiency, small heat, and the wiring is easy, not complicated.
Moreover, what is now 24 and also made 12-string, this approach is only suitable for isolated power supplies, non-isolated power supply does not apply. There are even some who do not understand the power of common sense do feel non-isolated power output constant current 600MA like cattle X, but in fact he did not put tubes in his carefully tried, not hot like this strange burst.
So, now do things like low-voltage high-current LED tube power supply, is actually the practice of trifles.
The basic structure of the buck power supply is in series with the inductor and the load voltage 300V, the switch switches, the load that is to achieve a voltage lower than 300V, the specific circuit a lot, a lot online, I do not say a draw. There are now 9910 on the market in general are basically constant current IC in this circuit to achieve. However, this circuit is the switch breakdown, the entire LED light board comes to an end, this should be regarded as the worst place. Because when the switch breakdown, the entire voltage of 300V across the lamp on the board, light board only had to bear more than a hundred volts, is now three hundred volts, and this one occurred. LED will certainly be burned. So many people say the insecurity of non-isolated, in fact, that buck, but because the vast majority of the general non-isolated step-down, so that the damage must be non-isolated bad LED. In fact, two other basic non-isolated structure, the power supply is damaged, will not affect the LED tube of.
Step-down power to design a small current into high voltage, efficiency can be high, elaborate as to why? Because high-pressure low-current, allowing the switch current pulse width larger, so the peak current is smaller, there is, the inductor losses are smaller, you can know through the circuit, the circuit is not convenient painting, concrete is difficult to re- described any longer. You just sum up, step-down power of the benefit is for 220 high-voltage input used to make the power device to withstand the voltage stress is small, suitable for big current output, such as doing 100MA current than the latter two to the easy, efficient higher. Efficiency as relatively high, the loss of the inductor is small, but large loss on the switch, because all through the power load must be transmitted through the switch, but the output power, only a portion through inductor, such as the 300V input, 120V output step-down power, only to go through the inductor portion 180V, 120V part is a direct conduction into the load, so that the inductor loss is relatively small, but the output power, all to go through the switch.
Non-isolated step-down power is the power structure is now widely used, accounting for almost a fluorescent lamp power supply 90 per cent. Many people think that only a buck non-isolated power supply one, often comes not isolated, think of Buck, we think that insecurity of light (referring to power damage). Buck is not just a matter of fact, there are two basic structures, namely the boost, and buck that BOOSTANDBUCK-BOOST two power supply even after the damage. LED tube light will not affect benefits. Buck power has its benefits, it is suitable for the 220 but not 110 as originally 110V voltage is low, a drop even lower, so the output current, low voltage, efficiency, do not be too high. 220V AC buck, about $ volt rectifier filtered through step-down circuit, generally down to the DC voltage of about 150V, so you can achieve high voltage low current output, high efficiency can be done. Generally to do with the MOS switch, the power to do this size, my experience is that you can do so almost ninety percent, then further is also difficult. The reason is simple, since the loss of the chip will be generally 0.5W to 1W and 10W fluorescent tube is about power, however. Beyond it is not possible. Now the power efficiency of this thing is true, many people are blowing, actually impossible to achieve.
Some people say 3W common power efficiency to achieve eighty-five%, and it is isolated type. Tell you, even hopping mode, the minimum no-load power consumption, but also what should 0.3W 3W output voltage can be to 85 per cent actually Seventy per cent considered very good, anyway, many people boast not scratch, you can live in layman flicker, but now understand the power of the LED's do not many.
I said, to high efficiency, first of all to do non-isolated, then the output of small size but also high-voltage current, eliminating the need for power devices conduction losses, so the LED power supply as a major loss of this one is its own chips loss, this loss is generally a few tenths of W to a W look, there is a switching losses, and to do with the MOS switch can significantly reduce this loss, with the transistor switching losses on a large lot. So try not to use the transistor. There is a small power supply, it is best not to be too provincial, not to use the RCC as RCC circuit is generally poor quality of the manufacturers simply do, in fact, the chip is cheap, ordinary switching power supply chip, integrated MOS pipe, but up to two dollars is not necessary if a little provincial, RCC only save some materials, in fact, higher processing costs such as repair, but worth the wait as the head.
Decomposition of two kinds of constant current control mode
The following saying is, the two constant current control mode switching power supply, resulting in two approaches. These two approaches, whether it is the principle, or device applications, and performance differences are quite large.
Said first principle. The first to present constant-current LED dedicated IC represented, mainly, such as 9910 series, AMC7150 all now playing the brand of LED constant current driver IC are basically this, and told him to constant current IC type it. But I think to do this so-called constant-current constant current IC, the effect is not how good. The control principle is relatively simple, is the primary power supply circuit, setting a current threshold, when the primary MOS turns on, then the inductor current is linearly increasing, up to a certain value when the time to achieve this threshold, the turn-off current, the next cycle is triggered by the trigger circuit conduction. In fact, this constant should be a limit, we know that when the inductance of a different time, primary current shape is different, although the same peak, but different from the current average. Therefore, as this power is generally mass-produced, the constant size of the consistency of very good control. There is a feature of this power, the output current is generally trapezoidal, that is, volatility-type current, electrolytic output is generally not smooth, this is a problem, if the current peak is too large, will have an impact on LED. If the power supply and output stage is not the kind of electrolysis current to smooth power, basically fall into this category. That is, to determine whether this is the control, to see there and on the output of electrolytic filter. I had this constant has been called the false constant, because its essence is a limit, not through op amp comparison, the obtained constant value.
The second constant current mode, switching power supply should be called a style. This control mode and constant voltage control mode switching power supply is similar. We all know that constant pressure to do it with a TL431, because it has an internal 2.5 V reference, and then use the resistor divider mode. When the output voltage is higher when, or low point, when you generate a comparison voltage, after amplification, to control the PWM signal, so this control can be very precise control of voltage. This control method requires a reference, but also an operational amplifier, if the base enough to accurately op amp magnification is large enough, then be very accurate. Similarly, do the constant is the need for a constant reference, an op amp, resistor overcurrent detection, as the signal, then the signal amplification, to control the PWM Unfortunately, now is not very good to find a very accurate reference signal, used of a transistor, the base to do a large drift, there is that you can take the diode conduction value of about 1V to do the benchmark, this may be not high, the best is when the TL431 op amp plus basis, but the circuit complex. However, this constant-current power supply, constant current control accuracy is better than. And this constant current mode control, the output will have to add electrolytic filter, so the DC output power is smooth, not pulsating, pulse, then it can not sample the. So to determine what kind as long as there is to see whether the output electrolytic on the line.
Two kinds of constant current control mode determines the use of two different types of devices, one to determine the two devices use different circuit, different performance, cost is also different. The 9910 series, represented by constant-current control IC to do LED tube lighting power, but the actual limit, control is relatively simple, strictly speaking, it does not belong to the mainstream switch mode power supply control, switch mode power supply control is certainly the mainstream have benchmarks and operational amplifier. However, this IC can only be used for LED is difficult to come out for other things, just because the LED on the requirements of very low ripple. But because it is only higher prices for LED so now. 9910 plus is the use of basic MOS pipe production, the output without electrolysis, in general I see a lot of people do is labor power conversion word inductance inductance. This power, the general information on the chip manufacturers have a map, are basically buck. I do not say, good at this much more than me.
Second, I represented, that is, the constant current control mode switching power supply drive. This is an ordinary switching power supply chip as the core conversion device, the chip a lot, such as the PI TNY series, TOP series, ST's VIPER12VIPER22 Fairchild's FSD200, and even with only MOS transistor or a tube of RCC, etc. can do. Advantage of low cost, reliability is good. Because the average price of switching power supply chip is not only good, but after extensive use are the classic products. In fact, as this IC is generally integrated MOS, MOS than the 9910 plus convenient, but control more complex, require the addition of constant current control device, you can use transistors or operational amplifier. Magnetic components can be inductive character of labor, can also be used with a gap of high-frequency transformer.
I love transformers, because the inductor while the cost is very low, but I do not think its load capacity, a sense of the amount of addition is not flexible adjustment. So I think a better device selection, the common integrated MOS chip plus high-frequency switching power supply transformer, from the performance, cost, and are the best choice, do not go to any constant current IC with the kind of thing, not easy to use, and expensive.
Finally, talk about, distinguish between the two power supplies, one of the most important way is to see whether the output of electrolytic capacitors for filtering.
Question whether it is done on the power limit control of power flow constant, or constant current power amplifier control, power supply problems to be resolved. Switching power supply chip that work when we need a relatively stable DC voltage supply for the chip, the chip operating current from one to several MA MA range. There is a chip such as FSD200NCP1012 and HV9910 is a high-pressure self-fed, it is easy to use, but the high-pressure feed, the IC heat rise, because the IC to withstand about 300V DC, as long as just a little current, even if a MA there are 0.3 watt consumption of the damage. General LED power supply, but ten watts or so, loss of a few tenths of watts of power efficiency can pull down a few points. There is a typical as QX9910. Pulldown resistor to take power, so that loss in the resistor, about which they have lost a few tenths of watts it. There is magnetic coupling, is to use the transformer, the main power coil plus a winding, as the auxiliary winding flyback power supply as to avoid loss of zero out of this a few watts of power. This is why I do not even use the isolating power transformer one of the reasons is that in order to avoid loss of a few tenths of watts of power, to mention a few points of efficiency.
About shape
Now T8 LED tube power supply, make light of the general requirements on the lamp manufacturers, such as the release T8 Led tube. Small part of the external. Do not know why to be so. In fact, difficult built-in power and performance is not good. But do not know why there are so many people make such a request. It may have been Suifeng Dao. External power supply should be said that more scientific, more convenient son. But I also had to Suifeng Dao, the customer what they want, I do. But do the built-in power supply, a considerable difficulty oh. Because the external power supply, the basic shape does not require, how much do want to do much, trying to do does not matter what shape. Built-in power supply, only made two, one is the most used, that is on the light board below, put the light board above, the following is power, power to do so requires very thin, or does not fit. Moreover, it can only components down, power on the line, only longer. I think this is not a good idea. But we generally like doing things like this. I do. There is less used, put both ends of that on the tube ends, so good to do, costs less. I have done, the basic shape is a two built-in.
Requirements for such power and circuit problems
My view is that, because the power supply to the built-in lights, the LED light and heat is the biggest killer of decline, so heat must be small, is certainly very high efficiency. Of course have to have high-efficiency power supply. T8 one meter long for the kind of two lights, it is best not to use a power supply, but with two, one at each end, the heat dispersion. So as not to make the heat concentrated in one place.
Depends on the efficiency of the power structure of the circuit and the use of devices. Said first circuit, some people said to isolate the power, I think is absolutely not necessary, because this kind of thing has always been placed within the body of light, people do not touch. Isolation is not necessary, because the efficiency of isolated power efficiency is lower than non-isolated, and the second is the best output to high voltage low current, so the power to make the efficiency high. Is now widely used, BUCK circuit, that is step-down circuit. It is best to do one hundred volts above the output voltage and current set at 100MA on it, such as driving one hundred and twenty, preferably three strings, each string of forty, is one hundred and thirty-volt voltage, current 60MA .
This power supply with a lot, I just think it is bad, if we pass out of control switch, LED will comes to an end. LED tube lighting now is so expensive. I am more optimistic about the boost circuit, the benefits of such a circuit, I repeatedly said, the first high-efficiency buck more than the second, bad power supply, LED lights will not be bad. This ensures fail-safe, if burned a power supply, but lost a few dollars, an LED lamp burning, the cost will be paid with a hundred dollars. I have the power devaluation or Boost.
There is, step-up circuit, it is easy to make a high PF value, the buck of the trouble some. I definitely boost circuit for the LED lamp has an overwhelming advantage or stronger than a buck. Only disadvantage of a year, that is the case of 220V mains input, load range is quite narrow, generally only for 100-140 a string or two strings of LED's for less than this number, or caught in the middle, but with inconvenient. But now do the LED lamp, 60CM long that are generally 100 to 140 one meter with two kind of general is to use two hundred to two hundred and sixty, as can still use the. So now LED lamp for general use is not isolated step-down circuit, there is no isolation step-up circuit, such circuit for LED lamps, should be regarded himself first.
I do switching power supply, the original did adapters, chargers, switching power supply steel. Then do the LED power supply, do 1W3W initially high power LED driver, but then do less. The reason is simple, there is no market. I found the power LED constant current power supply, as long as its power over 5W basically no market, only proof. Because the LED is too expensive. This, too, to make the power of peer-friends mind you, this is my voice of experience.
I do not know how many people stumble on the power LED Power LED thunder, rain, many victims lost their money in this one. Or low-power LED market a little better. But does not work, now in power LED driver, was resistive and capacitive step-down power accounts for most of the country. Constant current switching power supply drives the shape of a small power LED nice, but a lot of people can not accept the cost. I am a little over a constant-power LED drivers, switching power supply, efficiency, stability, reliability of 0.9, constant current accuracy is very good, the price was five dollars, but many people still Xiangui, because they take it and a dollar of RC Buck power to compare, of course, the two simply immeasurably. I do switch power inside, there is an integrated MOS switching power supply chip, and a transformer. This is the place where the cost of the two, of course, performance is put there. But I believe that the resulting low-power LED constant current driver will eliminate power RC Buck. Because consumers will gradually become more rational, step-down power to do a RC out of the lamp, almost no practical value, can only be a decoration and toys, if you really into the general LED lighting, down RC voltage power supply simply can not do the job. I can envisage the situation, with the improvement of LED performance, lower prices, power costs will be the LED lamps cost a very important part. The real lighting, RC Buck can not do the job. RC Buck popular power, but a transition, ultimately constant-current power supply authentic.
I am still optimistic about the current low-power LED lamps. Low-power LED lights, the key is too much bad light, the price is not ideal. But now, more than for general lighting or power advantage. I think that the low-power LED lamps into the general lighting, and energy-saving lamps under a high, is a matter within five years. The high-power LED into the general lighting, it is certainly something other than five years. So now I focus on R & D and small power LED production. I noticed a small power LED is now used in general lighting lamps are LED lamp, LED honeycomb lamps, LED lamp. In particular, the LED lamp, from the second half of 2007, many people began to develop, can be extremely hot. Basically, I am now looking for eight people in ten are doing this, so I do start to do LED fluorescent lamp power supply, do some time, so this talk about the power of R & D and production of general methods and principles. Individual experience to be above the bar.
