LED drive power main classification
The LED drive power is a voltage converter that converts the power supply to a specific voltage and current to drive the LEDs to emit light.
The following sections introduce the basics of classification, selection, and precautions for LED driver power:
First, the classification of LED drive power
(1) Constant current type:
a, the current output of the constant current drive circuit is constant, and the output DC voltage varies within a certain range according to the magnitude of the load resistance. The load resistance is small, the output voltage is low, and the load resistance is larger. The higher the voltage;
b. The constant current circuit is not afraid of load short circuit, but it is forbidden to completely open the load.
c, constant current drive circuit to drive LED is more ideal, but relatively high price.
d, should pay attention to the maximum withstand current and voltage value used, which limits the number of LEDs used;
(2) Constant pressure type:
a. When the parameters in the constant voltage circuit are determined, the output voltage is fixed, and the output current changes as the load increases or decreases;
b. The voltage regulator circuit is not afraid of the load open circuit, but it is forbidden to completely short the load.
c, driving the LED with a voltage-stabilized driving circuit, each string needs to add a suitable resistor to make each string of LED display brightness average;
d. The brightness is affected by the rectified voltage change.
Second, how to choose LED switching power supply
To ensure the safe use of LED switching power supplies, first select products with short circuit, overload protection and flame retardant function.
During the use of the LED switching power supply, the power supply may be ignited due to a short circuit, or may be damaged due to overload of the power supply (overload of the power supply).
The so-called short-circuit protection requires that the power supply be cut off in a very short time after the short-circuit fault occurs, protect the load from the impact of large currents, and effectively protect the safety of the LED switching power supply.
The overload protection requires the short-time overload current or short-circuit current of the LED switching power supply to instantaneously operate to protect the LED switching power supply.
Selecting the LED switching power supply, in addition to the short-circuit and overload protection functions, the flame-retardant function is another important barrier to protect the power supply.
Third, the use of precautions
To ensure the safety of LED switching power supply applications, in addition to selecting quality products that meet the standards, proper installation is the key.
There are three issues to be aware of when installing the power supply correctly:
1. Select the cable that meets the requirements of the national standard;
2. Pay attention to the correct connection method when connecting with the luminous characters;
3. The installation environment requirements of the power supply.
At present, the quality of cables in the domestic market is uneven. Many manufacturers sell copper-clad aluminum wire for profit, which will have great hidden dangers when used. The over-current capability will not work, resulting in excessive cable current overheating and fire, which will also harm the entire luminous word.
In the actual case, the choice of a suitable cable has a mouth: "2. 5 times multiplied by nine, go up one minus one", said that the various sections of copper core insulated wire of 2.5mm and below, the current carrying capacity It is about 9 times the number of sections. For example, a 2.5mm wire has a current carrying capacity of 2.5 & TImes; 9 = 22.5 (A). At the same time, the power supply output loop zero line should use a thicker cable than the output end.
In addition, many outdoor luminous characters are installed on the wall or at high altitude. Many of them are far away from the power supply, which also causes a problem: pressure drop.
The formula for calculating the line voltage drop is △U=(P*L)/(A*S), where: P is the line load, L is the line length, and A is the conductor material coefficient (copper is about 77, aluminum is about 46). S is the cable cross section.
Power installation environment:
The power supply should be installed in a ventilated environment as much as possible, which is conducive to its own heat dissipation. The air inlet and outlet should be kept within 10cm. The power supply should be installed in a fixed manner to prevent some accidents from causing the power supply to fall.
The power supply should be installed at a reasonable distance between the power sources to avoid being too close to each other to cause poor heat dissipation;
For the rain-proof power supply that is currently used in the market, it should be noted that the power supply should be installed more than 30cm above the ground and must be installed vertically.