Selection Method of Led Drive Power
Jul. 07, 2020
The load characteristics of the LED itself greatly affect the reliability of driving it with a switching power supply. The load characteristics of LEDs, that is, volt-ampere characteristics, are diode characteristics. Within a certain interval, the increase in the voltage across the LED causes its current to increase exponentially and explosively. Therefore, many LED lamps driven by switching power supplies show many unstable characteristics. 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 be regarded as stable.
The LED is very sensitive to voltage changes. When the LED is operating at a stable current, the voltage across the LED is generally between 3.0-3.6V (the power LED is slightly different). When the voltage across the LED fluctuates slightly, its The current at both ends will change drastically, and the output power of the power supply will also change drastically. If there is a relatively sudden increase in the grid voltage, and a small output voltage change at this time, a large output current will be created, and at this time, the power will increase sharply, and an accident will occur.
Practice has proved that adding various voltage suppression components, such as TVR, TVS, to the circuit is not very obvious. It will still be damaged when damaged. The reliability of the LED drive power supply cannot always be as good as other power supplies. This is Objective facts. Although many people say that there is no problem with the LED power supply they make, it is actually a pale and weak self-consolation, because he has not solved the fundamental problem.
Therefore, the current CE LED driver is generally isolated reliability is better than non-isolated, low voltage reliability is better than high voltage, it is under the constraints of this law, that is to improve efficiency, sacrifice In order to improve reliability, it is necessary to reduce efficiency.
Constant Current Led Driver
There are two types of driving methods for LED drive power:
(1) Constant current type:
1. The output current of the constant current LED driver is constant, but the output DC voltage varies within a certain range with the size of the load resistance. The load resistance is small, and the output voltage is low , The greater the load resistance, the higher the output voltage.
2. The constant current circuit is not afraid of load short circuit, but it is strictly forbidden to completely open the load.
3. The constant current drive circuit is ideal for driving LEDs, but the price is relatively high.
4. Pay attention to the withstand current and voltage used, which limits the number of LEDs used.
(2) Regulator type:
1. After the parameters in the voltage stabilizing circuit are determined, the output voltage is fixed, and the output current changes with the increase or decrease of the load.
2. The voltage stabilizing circuit is not afraid of open circuit of the load, but it is strictly forbidden to completely short circuit the load.
3. The LED is driven by a voltage-regulated driving circuit, and each string needs to be added with an appropriate resistance to make each string of LED display brightness average.
4. The brightness will be affected by the voltage change from the rectification.