S8050 low-cost high-performance LED constant current power supply circuit diagram

The constant current power supply method is an ideal LED power supply method. It can avoid current fluctuations caused by changes in the LED forward voltage. At the same time, the constant current stabilizes the brightness of the LED. Therefore, generally advanced LED circuits use the constant current method to drive the LED.

The circuit diagram below is a low-cost, high-performance LED constant current power supply circuit designed by Electronic Production Network;

When we design an LED drive power supply, we must know the LED current and voltage characteristics. Due to different LED manufacturers and LED specifications, the current and voltage characteristics are different. Taking the typical specifications of white LEDs as an example, according to the current and voltage changes of LEDs, the applied forward voltage is about 3.0-3.6V, the typical voltage is 3.3V, and the current is 20mA. Calculate I=2.5V/120=20mA according to the current and voltage in the circuit diagram; V=(3.3+3.3)/0.7=9.5v; Since the constant current accuracy of the circuit is very high, V can take a value between 10V-12V. This circuit also The current and voltage will be automatically stabilized at normal values. If the forward voltage applied to both ends of the LED exceeds 3.6V, the forward voltage will increase very little but the forward current of the LED may increase exponentially, causing the temperature of the LED emitter to rise, thereby accelerating the LED light attenuation and shortening the life of the LED. In severe cases, the LED may even be burned out. According to the voltage and current change characteristics of LED, strict requirements are put forward for the design of LED power supply . Designer: Mr. Lao Duo believes that although LED is more efficient than ordinary light sources in terms of energy saving, LED light sources cannot directly use the 220 grid voltage like ordinary light sources. It must be equipped with a dedicated power supply. Provide a dedicated LED power supply that can meet the rated voltage and current of the LED to keep the LED in the normal operating range. However, since the performance and conversion efficiency of LED power supplies with different specifications are different, choosing a suitable and efficient LED dedicated power supply can truly reveal the high-efficiency characteristics of LED light sources. Since the low-efficiency LED power supply itself consumes a large amount of power, the energy-saving characteristics of the LED cannot be displayed during the process of powering the LED. In short, LED power supply plays an important role in the stability, energy saving and lifespan of LED operation.

Due to its long environmental protection life, high photoelectric efficiency and many other advantages, LED applications have developed rapidly in various industries in recent years. LED power supplies have become a hot topic. Theoretically, the service life of LEDs is more than 100,000 hours. However, in practical applications, due to the design of the driving power supply Improper selection will accelerate the light decay of the LED, shorten its life, or even damage it. LED lighting products produced by many manufacturers use a resistor-capacitor voltage reduction plus a Zener diode to stabilize the voltage. This method of driving the LED to power the LED has shortcomings. The main reason is that the efficiency is low and a large amount of power is consumed on the voltage-reducing resistor, and it may even be possible. It exceeds the power consumed by the LED and cannot provide high current drive. Because the greater the current, the greater the power consumed on the voltage-reducing resistor. Therefore, LEDs of many products do not dare to be connected in parallel and use series connection to reduce the current. Secondly, the poor ability to stabilize the voltage cannot ensure that the current through the LED does not exceed its normal operating value. When designing products, the voltage at both ends of the LED is reduced to power the driver, which is at the expense of reducing the brightness of the LED. The brightness of the LED driven by the resistor-capacitor step-down method cannot be stable. When the power supply voltage is low, the brightness of the LED becomes darker, and when the power supply voltage is high, the brightness of the LED becomes brighter. The biggest advantage of driving LED using RC step-down method is low cost.

According to the characteristics of LED current and voltage changes, it is feasible to drive LEDs with constant voltage. Although commonly used voltage stabilizing circuits have the disadvantages of insufficient voltage stabilization accuracy and poor current stabilization ability, they may be overly precise in the application of some products. Its advantages are still irreplaceable by other driving methods. There is another LED driving method that is feasible. It is neither constant voltage nor constant current. However, through the design of the circuit, when the LED forward voltage increases, the driving current decreases, ensuring the safety of the LED product. Of course, the increase in forward voltage can only be within the tolerance range of the LED. If it is too high, the LED will be damaged. The ideal LED driving method is to use constant voltage and constant current, but the cost of the driver increases. In fact, each driving method has its advantages and disadvantages. According to the requirements and application scenarios of LED products, it is key to rationally select the LED power supply method and accurately design the power supply.