The LED power supply is completely different from the power supply of traditional lamps. First of all, the LED does not directly use the conventional grid voltage. In order to meet the special voltage and current requirements of the LED, special voltage conversion equipment must be designed according to the characteristics of the LED light source, and the LED can be normal. Work and different design methods will produce LED power supplies with different performance and conversion efficiency, so only high-efficiency power supplies can make LED light sources stably shine their biggest advantages, otherwise it will not be able to highlight the special energy saving of LEDs. Let's take a closer look at the knowledge of LED power supplies.

   First of all, LED power supply can be divided into two categories according to the driving method:

First, the constant current drive power supply:

(1) The output current of the constant current drive circuit is constant, but the output DC voltage varies within a certain range with the load resistance value. The smaller the load resistance value, the lower the output voltage, and the larger the load resistance value. , the output voltage will be higher;

(2) The constant current circuit is not afraid of short circuit of the load, but it is strictly forbidden to open the load completely.

(3) It is ideal to drive LEDs with a constant current drive circuit, but the price is relatively high.

(4) Pay attention to the maximum withstand current and voltage used, which limits the number of LEDs used;

Second, constant pressure type:

(1) After the parameters in the constant voltage circuit are determined, the output voltage is fixed, but the output current changes with the increase or decrease of the load;

(2) The constant voltage circuit is not afraid of the open circuit of the load, but the complete short circuit of the load is strictly prohibited.

(3) The LED is driven by a constant voltage drive circuit, and each string needs to be added with an appropriate resistor to make each string of LEDs display an average brightness;

(4) The brightness will be affected by the voltage change from rectification.

Others are divided into six categories according to the design structure of the circuit

(1) Resistor and capacitor step-down method: step-down through capacitor, when flashing is used, due to the effect of charge and discharge, the instantaneous current passing through the LED is extremely large, which is easy to damage the chip. Easily affected by grid voltage fluctuations, low power efficiency and low reliability.

(2) Resistor step-down method: step-down through resistors is greatly disturbed by changes in grid voltage, and it is not easy to make a regulated power supply. The step-down resistor consumes a large part of the energy, so this power supply method has low power efficiency. And the reliability of the system is also low.

(3) Conventional transformer step-down method: the power supply is small in size, heavy in weight, and low in power efficiency, generally only 45% to 60%, so it is rarely used and the reliability is not high.

(4) Step-down method of electronic transformer: the power supply efficiency is low, and the voltage range is not wide, generally 180~240V, and the ripple interference is large.

(5) RCC step-down switching power supply: the voltage regulation range is relatively wide, the power supply efficiency is relatively high, generally 70%~80% can be achieved, and the application is also wide. Because the oscillation frequency of this control method is discontinuous, the switching frequency is not easy to control, the load voltage ripple coefficient is relatively large, and the adaptability to abnormal loads is poor.

(6) PWM control mode switching power supply: It 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. The basic working principle of PWM switching regulator is that when the input voltage, internal parameters and external loads change, the control circuit performs closed-loop feedback through the difference between the controlled signal and the reference signal to adjust the pulse width of the main circuit switching device conduction. Make the output voltage or current of the switching power supply stable (ie, the corresponding regulated power supply or constant current power supply). The power supply efficiency is extremely high, generally 80%~90%, and the output voltage and current are stable. Generally, this kind of circuit has perfect protection measures and is a high-reliability power supply.

   In daily life, the voltage of household electricity in different regions and countries is different, mainly divided into two types, one is the European system, the voltage is 200-240V, 50HZ. Another American system is 110V, 60HZ, including Japan. The ordinary power supply is a wide voltage input of 90-264V. The dimming power supply is basically a narrow power supply. Half-drive power supply mode.