How to classify LED driver power supply

　　A. Constant current type:

　　1. Constant current drive circuit is ideal for driving LED , but the disadvantage is that the price is relatively high.

　　2. Although the constant current circuit is not afraid of load short circuit, it is strictly forbidden to completely open the load.

　　3. The output current of the constant current drive circuit is constant, but the output DC voltage varies within a certain range with the size of the load resistance.

　　4. Limit the number of LEDs used because they have maximum current and voltage values.

　　B. Voltage stabilization:

　　1. After the voltage stabilization circuit determines the various parameters, the output is a fixed voltage, but the output current changes with the increase or decrease of the load.

　　2. Although the voltage stabilizing circuit is not afraid of open-circuit load, it is strictly forbidden to completely short-circuit the load.

　　3. The voltage change after rectification will affect the brightness of the LED.

　　4. To make each string of LEDs driven by a voltage stabilizing circuit display uniform brightness, it is necessary to add appropriate resistance.

　　2. LED power supplies can be divided into six categories according to circuit structure:

　　1. Conventional transformer step-down:

　　The advantage of this type of power supply is its small size, but its disadvantage is that it is heavy and has a low power efficiency, generally between 45% and 60%. Because of its low reliability, it is rarely used.

　　2. Electronic transformer step-down:

　　The disadvantages of this power supply structure are low conversion efficiency, narrow voltage range (usually 180~240V), and large ripple interference.

　　3. Capacitor voltage reduction:

　　This type of LED power supply is easily affected by grid voltage fluctuations, has low power efficiency, and is not suitable for use when the LED is flashing, because the circuit uses capacitors to reduce voltage. When used in flashing mode, due to the effect of charging and discharging, the instantaneous current passing through the LED is extremely large, which can easily damage the chip.

　　4. Resistor voltage reduction:

　　This power supply method has low power efficiency and low system reliability. Because the circuit reduces voltage through resistance, it is greatly disturbed by the change of grid voltage, and it is not easy to make a voltage-stabilized power supply. In addition, the voltage-reducing resistance itself consumes a large part of the energy.

　　5. RCC step-down switching power supply:

　　The advantages of this type of LED power supply are wide voltage regulation range and high power efficiency, generally 70%~80%, and wide application. The main disadvantages are that the switching frequency is difficult to control, the load voltage ripple coefficient is large, and the load adaptability is poor in abnormal conditions.

　　6. PWM controlled switching power supply:

　　At present, the LED power supply designed with PWM control method is more ideal, because the output voltage or current of this switching power supply is very stable. The power conversion efficiency is extremely high, generally up to 80%~90%, and the output voltage and current are very stable. It is especially suitable for driving power supply of LED street lamps . This type of LED power supply is mainly composed of four parts: input rectification and filtering part, output rectification and filtering part, PWM voltage regulation control part, and switching energy conversion part. Moreover, this circuit has perfect protection measures and is a high-reliability power supply.