FAQ
FAQ

LED lamp power supply design ten key

发布日期:2015-09-09
LED lamp power supply design ten key
Preface
LED light-emitting diode is a semiconductor light-emitting diode, fully equipped with semiconductor properties. Non incandescent lamp, energy saving fluorescent lamp characteristic, life length, temperature and current has a direct relationship, the size of the current and the voltage is nonlinear relationship, the LED lamp should be constant current source to ensure the service life of the whole lamp, the light fades. The size of the current varies with the LED property. This is the LED Engineer in the design should pay attention to matters.
1, LED lamp power supply why must constant flow of it /
The characteristics of LED semiconductor material determine that it is influenced by the environment, such as temperature change, LED current will increase, and the increase of voltage, the current of LED will also increase. Long exceed the rated current, will greatly shorten the service life of the LED lamp. And LED constant current is the change in the temperature and voltage and other environmental factors, to ensure that the work of the current value of the same.
2, LED lamp power to what can be matched with the lamp board?
Some customers first design a good light board, and then find power, found that it is difficult to have a suitable power supply, or the current is too large, voltage is too small (such as 7X1WI 350mA, or V 20V); or the current is too small, too high (such as I 200mA or V 25V), resulting in a serious heat, low efficiency, or input voltage range is not enough. In fact, choose one of the most excellent string and connection mode, plus the voltage on each LED is the same, while the power of the effect can play the best performance. The best way is to first and power manufacturers to communicate, tailored. Or their own production power.
3, LED lamp power supply of the working current is the most appropriate
For example, the rated operating current of 350 Ma LED, and some factories have used to do the first, design 350 Ma, in fact, the current heat is very serious, after many trials, design 320 Ma is more ideal. Reduce heat, so that more power into visible light.
4, LED lamp power supply of working voltage
General LED recommended operating voltage is 3.0-3.5V, after testing, most of the work in the 3.2V, so the 3.2V calculation formula is reasonable. The total =3.2* N N voltage lamp series
5, LED lamp series parallel connection and wide voltage to how wide it?
To make the LED lamp work in a wide range of input voltage range AC85-265V, the LED series parallel mode of the lamp board is very important. Try not to use wide voltage, can be divided into AC220V, AC110V as far as possible classification, so as to ensure the reliability of power. Since the current power supply is generally non isolated constant current power supply, the output voltage is not more than 70V, the series number is no more than 23 strings in the required voltage 110V. The output voltage can reach 156V when the input voltage is 220V. That is to say, series number not more than 45 strings. Parallel number not too much, otherwise the work current is too large, power supply heat. There is also a wide voltage program, APFC active power compensation is the first to use L6561/7527 to raise the voltage up to 400V, and then buck, equivalent to two switching power supply. This scheme is used in certain conditions.
6, LED series parallel with PFC power factor
Isolated input AC220V high voltage terminal electrolytic capacitor is generally 1W=1UF, AC110V1W=2UF current market power PFC has three kinds of situations: one is non power factor compensation circuit, its PF value is generally around 0.65; the two is passive power factor compensation PFC circuit, which is the most widely used, PF value is generally 0.92 or three is active power factor compensation, known as APFC AC220V, AC110V can use the same capacity electrolytic capacitor, 1W=1.5UF. PF value can reach 0.99, but the cost of this scheme is more than second kinds of schemes for your one times the reliability of the poor. So more of the second programs. For passive PFC circuits: also called the PFC circuit, the DC operating voltage range is half the peak of the AC input voltage. If the input is 220V, the peak value is 220*1.414=312V, and the half of the peak voltage is 156V, and the output wave is not the half wave
So the LED lamp number 45 on the following series is appropriate. Therefore, in order to obtain the relatively large power factor, beads series number can not be too small, otherwise it is not up to the best working state, in isolated power series number and secondary winding turns on, must to do the power to meet the power output. In the rated voltage of the electronic component, the smaller the working current of the electric element, the longer the life of the bottom of the heat is, the shorter the life will be. LED lamp is very sensitive to the exchange amount, the higher the light weight exchange comfort is worse. General to use electrolytic capacitors to maintain the voltage, as far as possible to reduce the output voltage AC, the end of the end of the electrolytic capacitor capacity can not be too small, capacity and output current ratio of 1UF to 1.5MA or LED will flash. Non isolated input terminal high voltage electrolytic capacitor selection and isolation, the output terminal capacitor 6MA 1UF. LED power supply at the output end of the electrolytic capacitor to meet 1UF 0.5MA.
7, LED lamp power supply constant current accuracy
On the market, the constant current accuracy of the power supply is poor, and the constant flow of the recommended scheme, such as the market, is 8%, and the error is too large. General requirements in 3% can be. Press 3% of the design plan. Production power to be fine tuned to achieve + 3% error.
8, isolation / non isolation
General isolation power supply such as 15W, placed in the LED tube, the transformer is very large, it is difficult to put in. Mainly depends on the specific circumstances of the spatial structure, the general can only do 15W, more than 15W