Low cost and high performance LED constant current power supply

Low cost and high performance LED constant current power supply

LED has been rapidly developed in various industries in recent years due to its many advantages such as environmental protection, long life and high photoelectric efficiency. LED power supply has become a hot topic. Theoretically, the service life of LED is more than 100,000 hours, but in actual application, due to improper design of the driving power supply, the LED light decay is accelerated, the life is shortened or even damaged.
Constant current power supply is an ideal LED power supply method. It can avoid the current fluctuation caused by the change of the LED forward voltage. At the same time, the constant current makes the brightness of the LED stable. Therefore, the general advanced LED circuit uses constant current to drive the LED.
The following circuit diagram is a low-cost and high-performance LED constant current power supply circuit designed by the electronic production network;
when we design the LED driving 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 light LED as an example, according to the current and voltage change law of LED, the forward voltage is about 3.0-3.6V, the typical value voltage is 3.3V, and the current is 20mA. According to the current and voltage in the circuit diagram, I=2.5V/120=20mA; V=（3.3+3.3）/0.7=9.5v; Since the constant current accuracy of the circuit is very high, V can be set at 10V-12V, and the circuit will automatically stabilize the current and voltage at normal values. If the forward voltage applied to both ends of the LED exceeds 3.6V, the forward voltage increases very little, but the forward current of the LED may increase exponentially, causing the temperature of the LED light source to rise, thereby accelerating the LED light attenuation, shortening the life of the LED, and even burning the LED in severe cases. According to the voltage and current variation characteristics of the LED, strict requirements are put forward for the design of the LED power supply. Designer: Mr. Lao Duo believes that although LED is more efficient than ordinary light sources in energy saving, LED light sources cannot directly use 220 grid voltage like ordinary light sources, and they must be equipped with a dedicated power supply. Only by providing a dedicated LED power supply that can meet the rated voltage and current of the LED can the LED be in the normal working range. However, due to the different performance and conversion efficiency of LED power supplies of various specifications, choosing a suitable and efficient LED power supply can truly reveal the high-efficiency characteristics of LED light sources. Since the low-efficiency LED power supply itself consumes a lot of electricity, the energy-saving characteristics of LED cannot be displayed in the process of powering the LED. In short, LED power supplies play an important role in the stability, energy saving and life of LED work.
Due to the many advantages of LED, such as environmental protection, long life and high photoelectric efficiency, it has been rapidly developed in various industries in recent years, and LED power supplies have become a hot topic. In theory, the service life of LED is more than 100,000 hours, but in actual applications, due to improper selection of the design of the driving power supply, the LED light decay is accelerated, the life is shortened or even damaged. Many manufacturers produce LED lighting products, which use a resistor-capacitor voltage reduction and a voltage regulator diode to power the LED. This way of driving LEDs has defects, mainly because of low efficiency, large amounts of electricity are consumed on the voltage-reducing resistor, and it may even exceed the electricity consumed by the LED, and it cannot provide high current drive, because the larger the current, the greater the electricity consumed on the voltage-reducing resistor, so many products dare not use the LED in parallel, and use the series method to reduce the current. Secondly, the poor ability to stabilize voltage cannot ensure that the current through the LED does not exceed its normal working 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 RC step-down method cannot be stable. When the power supply voltage is low, the brightness of the LED becomes dim, and when the power supply voltage is high, the brightness of the LED becomes brighter. The biggest advantage of driving LEDs
by the 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 the commonly used voltage stabilization circuit has the disadvantages of insufficient voltage stabilization accuracy and poor current stabilization ability, it may be over-precisely designed in the application of some products, and its advantages are still irreplaceable by other driving methods. There is also a feasible LED driving method, which is neither constant voltage nor constant current, but through the design of the circuit, when the forward voltage of the LED increases, the driving current is reduced, ensuring the safety of the LED product. Of course, the increase in forward voltage can only be within the tolerance range of the LED, and too high will also damage the LED. 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 crucial to reasonably select the LED power supply method and accurately design the power supply.