The previous LED lamps used constant voltage power supply. At that time, they did not understand the performance of the LED. According to the data given by the manufacturer, each small lamp bead was given 20MA. After our test, the lamp bead was always burned, and the manufacturer’s data was known. Unreliable, we have reduced current usage. At that time, in 2002, I made some applications such as MR16 small light bulbs and billboards. I started to do constant current drive in 2007, what HV9910, PT4107, PT6901, SN3910, IR, and more tests, but the first success is QX9910, some goods have been sold, but QX9910 has many bad products, after aging The products are also not stable, there are often flashing lights, and there are still some remaining souvenirs. I think that if you want to be a good driver, you should first find a chip.
At the beginning of 2007, constant current IC was difficult to find, and the price was also expensive. A HV9910 would cost 8 yuan, and an IR S2540 would cost 25 yuan. In fact, it was a half-bridge chip, which was used to swear, and what Japan Some of the chips are also used to swear. In fact, they are ordinary constant voltage ICs. I have been detouring on these boring chips for a long time, which has seriously affected the progress.
The HV9910 series is also very popular in the second generation of ICs, but for technical reasons, high voltage directly into the IC, easy to bomb. Later, a lot of imitations came out. The best example is SMD802, which has multiple output short-circuit protections. It has been widely used. With the replacement, this IC is now out of date.
A lot of ICs have not died before they are officially put into production.
In 2009, the BP2808 was introduced. This non-isolated IC has been used for several years. It is difficult to make a power supply for 1000 pieces. Because the BP2808 is a third-generation IC with stable performance, it can output more than 30W. Power, and long-term use, more efficient, easy 95%.
This kind of driver chip has a common shortcoming, that is, EMCT EMI is not good. After long-term exploration, we believe that adding two differential mode inductors at the input end of MOS power can solve EMC, and there are several solutions for EMI. Add a magnetic bead to the drain of the MOS tube, but this method increases the loss in exchange for it. My method is to add more than 100P ceramic capacitor to the drain source (SD). This method can Effectively improve efficiency and control EMI.
Jingfeng is constantly advancing, and now it has introduced BP3105. In the wide voltage range, the constant current accuracy is 1%, which defeats all domestic and foreign solution companies. The first domestic dimming constant current IC: BP3109 is also good. Its design is that the brightness is cut off under certain conditions, avoiding the flashing phenomenon and the cost is very low. I heard that there is a better IC launch in the second half of the year.
BP2808 is also copied, but Jingfeng Mingyuan has now adjusted the price. The third and second hairs are still stable with the original factory. This imitation IC has a problem when it supplies samples. The test four burned two lights. Board, there are a few that promote me to me, I dare not use it.
But now the cheapest IC in China is core-connected, and the CL1100 primary control small power supply, adapt to the lamp cup series. Core Alliance is started by copying board, so the cost is low, so the price is cheap, the performance is acceptable, the stability is also very good, so the shipment is very large, and it is also one of the most popular chips. Of course, the company also has more High power chip.
GR8210, a product of Taiwan's Luda Company, performed well during the test, and its efficiency and power factor were very good. It improved EMC on the basis of BP2808, but it was not ideal in the case of large shipments. There are more than 10% of defective products inside. In addition, the same series connection method, when the number of parallel changes, the inductance must also be changed, so the requirements for the inductance are extremely high, the advantage is that the EMC is internally controlled and easily over EMC. The cost of this kind of IC is relatively high, and there are not many mass productions yet. It is not suitable for water and soil.
The low-cost DC-DC has the lowest cost of MC34063. A chip is only 0.23 yuan. After using it, it is 3*1W. 1*3W is not bad. It is hard to say that the current is big.
This primary-side drive circuit was first developed by the US IWTT company. It is recognized that the performance is the most stable and the cost is not high, but the domestically produced chips of comparable performance have been successively produced. The IW3620 is better than the L6562.
There are still many domestic and foreign companies, and there are hundreds of them. There are original ones and some imitations. There are some things I know to do well.
Angbao: Some products such as OB2203, 2263 are easy to use, but I heard that some engineers are not successful, and there are occasional bombings, but I think this chip is still good. If you can't do it, you can't blame the chip. achieve.
Xinpeng, Silan Micro is a famous factory, and has launched several functional chips. Many companies have made L6561 and (L6599) half-bridge chips, and most of them are still very useful.
Why is the efficiency of this non-isolated chip after testing not as efficient as DEMO?
What are the components that do not isolate the power supply that affect efficiency?
First: the freewheeling diode, the internal resistance of this diode directly affects the efficiency. My multimeter diode is 25°C and the measurement is 400 or less. When the temperature is high, the internal resistance of the diode is lower.
However, it takes a lot of trouble to find a diode. Many manufacturers' diodes do not meet the requirements. The price is high and low, and the difference is doubled. Later, a low-quality and good-quality merchant was found, which is the manufacturer's counter.
Inductance: The core and wire diameter of the inductor are very important. Don't underestimate this component. Its quality also determines the success or failure. Try to use a larger volume. The wire diameter should be as thick as possible. The resulting internal resistance will be small and the efficiency will be high. . Do not use those copper-clad aluminum wires.
MOS tube: For example, to make a power supply of about 20W, the current is about 0.2 at 85V, and it is enough to use 1N60, but in order to improve efficiency, I use 4N60, ​​this chip is several times larger than 1N60, and the internal resistance is small. More, the heat is not as high as 1N60, but pay attention to some counterfeit and shoddy products when purchasing, first use a multimeter to judge, use diode to measure the resistance between DS, 4N60 resistance is about 500, if greater than This figure is considered to be a small or unqualified product.
Sometimes you can consider using 10N60 for 20W or more, so the efficiency will be higher.
There is also a layout process. The distance between the power supply and the power supply can not be too long. If it is long, the loss of high-frequency signals will increase a lot. If the line is long, the filter should be installed in a very close place.
Layout process:
When there is interference in the layout, it affects the power very much. Some powers are not big, or the heat is serious. When the interference signal is zero-crossing, the current on the inductor cannot be released. Overheating occurs after a large sampling resistor.
The ground wire and power cable should be as thick as possible, and some free places should be grounded to shield and absorb the space signal.
This kind of driver board must use the FR-4 fiberboard, because this board is also very good in heat dissipation. When using the board, the copper thickness should be more than 1AS, so the current is very smooth. These are all related to efficiency and reliability.
In fact, the components we use have some temperature characteristics. When the temperature is high, the parameters of the components themselves will change a little. Of course, the components have the characteristics of positive temperature and negative temperature coefficient. When buying some components, especially resistors, ask Manufacturers, in order to arrange on the circuit when in use.
As for the life of the LED power supply, many people think that the life of the electrolysis marked is the life of the LED power supply. This argument is unfounded. Some people have watched television for decades at home. Until now, there is no bad, and there is no electrolysis. Changed, why can I still work? The answer is that electrolysis will not affect the life. In the past few years, the electrolysis was best only 2000H, and now the electrolysis is above 2000H. We use the electrolysis of 3000-5000H. We have solved the problem by increasing the capacity during design. The electrolysis of the manufacturer is to ensure the data of this time capacity. The electrolytic solution is dry bit by bit, and will maintain a certain capacity later in life, generally will not affect use.
Electrolysis like the old-fashioned tube radio does not work. It will be replaced in the next three or two years. At that time, the process could not be compared with the present. It was a paper tube and a yellow wax package. Later, aluminum electrolysis appeared, and the life would be longer, but it would not. More than 1000 hours. I think the average electrical life will not be less than 10 years.
Edit: Xiang Zuo
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