In short,LED drive is also a kind of power transformer, only it has a few aspects of uniqueness, but also the relevance of the power transformer, so it is used to classify it as LED drive. These aspects are unique:
1. Its voltage output is a multiple of 3.2, that is, the voltage output form is 3.2V, 6.4V, 9.6V, 12.8V...... , but generally not more than 25.6V, because after this number, when the LED is turned on, due to poor product integrity, there will be the possibility of burning the LED last turned on instantly. This voltage is not constant, but varies with the load.
2, its output current is stable, the ideal power supply circuit is no matter how the LED characteristics curve changes, the LED driver current maintenance will not change. But limited to the precision of components, there will still be a small amount of change, and this change is also the key parameter to distinguish whether the optocoupler circuit is excellent. The on and off of LED and the culvert number of the working voltage is a "three-section" association of a discrete system, so it is very critical to maintain constant current power supply.
3. The startup is soft. Since the consistency of leds is very poor, the activity of the internal PN junction changes instantaneously when the leds are turned on, and the leds' drivers are usually designed for soft start to avoid this defect.
4. Its circuit requirements are the simplest, because in many cases, the circuit is required to be installed in a very small space to match the convenience of LED lighting, so the circuit should be as simple as possible, so as to save costs and reduce energy consumption.
5, it is generally not protection regulation, because many goods is similar as the structure of the general lighting lamps and lanterns, safety level and lighting lamps and lanterns is almost, but this is a "reader", article 5 guys in the case of a master don't have to have a misunderstanding, because some drive or must protection, this feature is only applicable to everyone up to date at this stage of the power circuit, not necessarily appropriate After the development trend of power supply circuit must.
To sum up, soft start, constant current, step voltage and simple circuit are its characteristics
Here again emphasize a point: very from the side of the constant current power supply, but the mouth does not mention the working voltage, is not right, because the definition of constant current power supply and working voltage irrelevant, such as a switching power supply, if it is only 30V output constant current power supply, then if you lead the case, The working voltage is 30V, at this time if you connect the LED, then the immediate use of PN junction in the work of the components, will be burned before the most accurate reflection of the power supply circuit, because all the power supply circuit must have reaction speed, and the power supply circuit in the work. The device is a semiconductor, all PN junction only in the power supply to give a sampling signal after the reaction, and the LED PN junction directly began to work, so its "reaction" than the circuit in the "multiple PN junction with" faster, and ahead of combustion! . But this kind of drive is also used in special occasions, but this LED drive does not allow the output end to be open. To be exact, "LED is not allowed after the output is open." Therefore, the concept of voltage must be added at the same time of constant current, which is more conducive to understanding the LED conduction function curve.
In fact, LED driven switching power supply is also a power transformer, because it has many characteristics of the power transformer; The difference is that LED driven switching power supply is generally constant current power output, and the traditional power transformer is generally constant current source, is often said power switch adjustable voltage power supply; LED driven switching power supply can also be considered as a special power transformer