First of all, we must know what is the LED drive power? The following is a professional LED power supply manufacturer-Bineng Electronics for everyone to introduce:
LED drive power is a voltage converter that converts the power supply into a specific voltage and current to drive the LED to emit light. Under normal circumstances, the input of the LED driving power supply includes high-voltage power frequency AC (that is, commercial power), low-voltage DC, high-voltage DC, and low-voltage high-frequency AC (such as the output of an electronic transformer). The output of the LED drive power supply is mostly a constant current source that can change the voltage as the forward voltage drop of the LED changes.
The core components of the LED power supply include switching controllers, inductors, switching components (MOSfet), feedback resistors, input filter devices, output filter devices, and so on. According to the requirements of different occasions, there must be input overvoltage protection circuit, input undervoltage protection circuit, LED open circuit protection, overcurrent protection and other circuits.
LED power supply can be divided into two categories according to the driving method:
A. Voltage regulation type:
1. When the voltage regulator circuit determines various parameters, the output is a fixed voltage, but the output current changes with the increase and decrease of the load
2. Although the voltage-stabilizing circuit is not afraid of open load, it is strictly forbidden to completely short-circuit the load
3. The brightness will be affected by the rectified voltage change
4. To make each string drive the LED display voltage uniformly with a voltage stabilizing circuit, it is necessary to add a suitable resistance
B. Constant current type:
1. Constant current drive circuit is ideal for driving LED, but relatively expensive
2. Although the constant current circuit is not afraid of short circuit of the load, it is strictly forbidden to completely open the load
3. The current output by the constant current drive circuit is constant, but the output DC voltage varies within a certain range with the size of the load resistance. The load resistance is small, the output voltage is low, and the larger the load resistance, the output The higher the voltage.
4. Limit the number of LEDs used because it has the maximum withstand current and voltage
LED power 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 it is biased and the efficiency is also very low, generally 45% to 60%, because the reliability is not high, so it is generally seldom used.
2. Capacitor buck:
This type of LED power supply is easily affected by the fluctuation of the grid voltage, and the power supply efficiency is low. It is not suitable for the LED to be used during flashing, because the circuit is stepped down through the capacitor. Very large, easy to damage the chip.
3. Electronic transformer step-down:
The disadvantage of this power supply structure is low conversion efficiency, narrow voltage range, generally 180 ~ 240V, and large ripple interference.
4. Resistance drop:
This power supply has low power efficiency and low system reliability. Because the circuit is stepped down by the resistor, it is greatly disturbed by the change of the grid voltage, and it is not easy to make a regulated power supply, and the step-down resistor itself also consumes a large part 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, generally 70% to 80%, and the application is wide. The disadvantages are that the switching frequency is not easy to control, the load voltage ripple coefficient is large, and the load adaptability is abnormal in abnormal situations.
6. PWM controlled switching power supply:
At present, the LED power supply designed by the 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. This type of LED power supply is mainly composed of four parts: input rectification and filtering part, output rectification and filtering part, PWM Voltage stabilization control part, switching energy conversion part. And this circuit has perfect protection measures, which belong to high reliability power supply.