How to select the appropriate LED driver power supply

The load characteristics of LED greatly affect the reliability of switching power supply. The load characteristics of LED, namely the volt ampere characteristic, belong to the diode characteristic. Within a certain range, the voltage of the LED increases, so that the current growth is exponential, explosive growth. Therefore, a lot of switching power supply LED lamps, showing a lot of instability. The reason is that the output of the switching power supply is not very clean and smooth DC voltage (current) energy, but a very complex energy signal, which can generally be seen as a smooth.

LED is very sensitive to voltage changes, LED in stable working current, the voltage is usually between 3.0-3.6V (the size of the power LED is slightly different), when added at both ends of the voltage fluctuate slightly after the two ends of the current will be dramatic changes, while the power supply output power is also drastic changes. If there is a sudden increase in the voltage of the grid, at this time a small output voltage changes, it will create a large output current becomes larger, this time the power surge, the accident occurred.

Practice has proved that in the circuit, adding various voltage suppression elements, such as TVR, TVS, all kinds of anti - * *, the effect is not very obvious, the damage will damage the reliability of LED driver always do the other power so good, this is an objective fact. Although many people say how to do their own LED power is no problem, it is actually a weak self consolation, because he did not solve the fundamental problem.

The reliability and the efficiency are mutually restricted, the high efficiency power supply, the reliability must be reduced, and the reliability is improved. To reduce the influence of the input voltage on the output voltage, the electrical energy must be converted to multiple layers. For a simple example, usually BUCK circuit reliability is not too high, but the BUCK-BOOST circuit, reliability is better than BUCK, which is tested by practice. Because to understand power principle of people know that the BUCK circuit in the switch, LED load and inductance is 300V high voltage on the LED at this time is powered directly by 300V, and the BUCK-BOOST circuit at this time is to separate the inductance energy storage impulse, during shutdown, the BUCK circuit is to load inductance current. The BUCK-BOOST circuit is turned off, the energy transfer to the inductive load of LED. The difference is, BUCK circuit for a period of time, is the direct use of 300V power supply, which is the first in the inductor, and then from the inductive energy transfer to LED load, so the latter because of its high reliability, after the long way round. The way of transmission is long, also can make the efficiency is reduced, the efficiency of general BUCK-BOOST circuit is lower than BUCK circuit 2-5 percentage points.

So now the LED drive power, general reliability is higher than the non isolated isolation, high reliability is higher than the low, it is in the control law, which improves the efficiency of sacrificing reliability, improve reliability, to reduce efficiency.

In fact, the problem is caused by the load characteristics of the LED, the fundamental way is to improve the load characteristics of the LED lamp string, but the improvement of the load characteristics of the method is still sacrifice efficiency as a means. The easiest way to improve the load characteristics is to string the resistance in the LED string, the greater the resistance string, the more stable the load characteristics. Of course, this is to reduce efficiency. There is also a good way, is to use linear manostat, triode, adjustment tube, transistor resistor is equivalent to a variable, in this case, the reliability should be higher (that I have no experience in theory). Therefore, the basic can be judged, the most reliable method of driving the LED is in fact: ordinary constant voltage power supply and linear constant current device, of course, efficiency is not too high. A high efficiency, reliability down.