一、LED power can be divided into two categories according to the driving method:
A.Constant current type:
1、The constant current drive circuit drives the LED is ideal. The disadvantage is that the price is higher.
2、Although the constant current circuit is not afraid of load short circuit, it is forbidden to completely open the load.
3、The current output by the constant current drive circuit is constant, and the output DC voltage varies within a certain range depending on the magnitude of the load resistance.
4、To limit the number of LEDs used, because it has the maximum withstand current and voltage values.
1、After the voltage regulator circuit determines the parameters, the output is a fixed voltage, and the output current changes with the increase or decrease of the load.
2、Although the voltage regulator circuit is not afraid of the load open circuit, it is forbidden to completely short the load.
3、The rectified voltage change will affect the brightness of the LED.
4、In order to make each string with a voltage regulator circuit to drive the LED display brightness uniform, you need to add a suitable resistor.
二、LED power supplies can be divided into six categories according to the circuit structure:
1、Conventional transformer step-down: The advantage of this kind of power supply is small size. The disadvantage is that the weight is heavy and the power supply efficiency is very low. It is generally 45%~60%. Because the reliability is not high, it is rarely used.
2、Electronic transformer step-down: This power supply structure is inefficient, low conversion efficiency, narrow voltage range, generally 180~240V, and large ripple interference.
3、Capacitor buck: This type of LED power supply is easily affected by grid voltage fluctuations, and the power supply efficiency is low. It is not suitable for LEDs to be used when flashing, because the circuit is stepped down by the capacitor, and when it is used for flashing, it is passed due to charge and discharge. LED instantaneous current is very large, easy to damage the chip.
4、Resistor step-down: This kind of power supply mode has low power efficiency, and the reliability of the system is also low. Because the circuit is stepped down by the resistor, it is greatly interfered by the change of the grid voltage, it is not easy to make a regulated power supply, and the step-down resistor itself It also consumes a lot of energy.
5、RCC step-down switching power supply: This type of LED power supply has the advantages of wide voltage regulation range and high power supply efficiency. Generally, it can be used in 70%~80%. It is widely used. The main disadvantage is that the switching frequency is not easy to control, and the load voltage ripples. The coefficient is large, and the load adaptability is abnormal.
6、PWM control type switching power supply: At present, the LED power supply designed by PWM control mode is ideal because the output voltage or current of this switching power supply is stable. The power conversion efficiency is extremely high, generally up to 80%~90 %, and the output voltage and current are very stable. Especially suitable for the driving power of LED street lamps. The LED power supply in this way is mainly composed of four parts: input rectification filtering part, output rectification filtering part, PWM voltage regulation control part, switching energy conversion part. Perfect protection measures are high reliability power supplies.