First, LED power can be divided into two categories according to the driving method:
A. Constant current:
1.Constant current drive circuit is ideal for driving LEDs.The disadvantage is that the price is higher.
2.Although the constant current circuit is not afraid of short circuit of the load, it is strictly prohibited that the load is completely open.
3.The current output by the constant current drive circuit is constant, but the output DC voltage changes within a certain range with the size of the load resistance.
4.It is necessary to limit the number of LEDs used because it has the maximum current and voltage value.
1.After the voltage stabilization circuit determines various parameters, the output is a fixed voltage, but the output current changes as the load increases or decreases.
2.Although the voltage stabilization circuit is not afraid of the open circuit of the load, it is strictly forbidden to completely short the load.
3.The voltage change after rectification will affect the brightness of the LED.
4.To make each string drive the LED display brightness uniform with a voltage stabilization circuit, you need to add a suitable resistor.
What are the categories of LED drive power
LED power supplies can be divided into six categories according to the circuit structure:
1.Conventional transformer buck:
The advantage of this type of power supply is its small size.The disadvantages are its heavy weight and low power efficiency, which is generally 45% ~ 60% .Because its reliability is not high, it is rarely used.
2.Electronic transformer buck:
The disadvantages of this power structure are low conversion efficiency, narrow voltage range, generally 180 ~ 240V, and large ripple interference.
The LED power supply in this way is easily affected by the voltage fluctuation of the power grid, 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 capacitors. During flashing use, due to the charge and discharge effect, the instantaneous current through the LED Extremely large and easy to damage the chip.
This power supply method has low power efficiency and low system reliability. Because the circuit is stepped down by resistors, it is more affected by changes in the grid voltage, so it is not easy to make a regulated power supply, and the step-down resistor itself consumes a lot of power. Most of the energy.
5.RCC step-down switching power supply:
The advantages of this type of LED power supply are that the voltage regulation range is relatively wide and the power supply efficiency is relatively high, which can generally be 70% ~ 80%, which is widely used. The disadvantages are mainly that the switching frequency is not easy to control, the load voltage ripple coefficient is large, and the load is abnormal. Poor adaptability.
6.PWM controlled switching power supply:
At present, the LED power supply designed by PWM control method is ideal, because the output voltage or current of this switching power supply is very stable. The power conversion efficiency is extremely high, which can generally be as high as 80% ~ 90%, and the output voltage, The current is very stable. It is especially suitable for the driving power of LED street lights. The LED power supply in this way is mainly composed of four parts: input rectification filter part, output rectification filter part, PWM voltage control part, and switching energy conversion part. All circuits have perfect protection measures and belong to high reliability power supply.