With the increasing application of LED, the performance of LED driving power will be more and more suitable for LED requirements.

1. According to the driving method, it can be divided into two categories:

(1) Constant current

(2) Constant pressure

a. The output current of the constant current drive circuit is constant, but the output DC voltage changes within a certain range according to the size of the load resistance. The smaller the load resistance, the lower the output voltage, and the larger the load resistance, the output The higher the voltage;

b. The constant current circuit is not afraid of short circuit of the load, but it is strictly prohibited that the load is completely open.

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

d. Attention should be paid to the maximum withstand current and voltage value, which limits the number of LEDs used;

(2) Regulated type:

a, after the parameters of the voltage regulator circuit are determined, the output voltage is fixed, but the output current changes with the increase and decrease of the load;

b. The voltage stabilization circuit is not afraid of the open circuit of the load, but it is strictly forbidden that the load is completely short-circuited.

c. The LEDs are driven by a voltage-stabilized driving circuit. Each string needs to be added with a suitable resistor to make each string of LEDs display an average brightness;

d. Brightness will be affected by voltage changes from rectification.

2.Classify by circuit structure

(1) Resistor and capacitor step-down method: The capacitor is used to step down the voltage. During flashing use, due to the charge and discharge effect, the instantaneous current through the LED is extremely large and the chip is easily damaged. Susceptible to power grid voltage fluctuations, low power efficiency and low reliability.

(2) Resistance step-down method: The resistance step-down method is greatly affected by the change of the 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 the power supply efficiency of this method is very low , And the system is also less reliable.

(3) The conventional transformer step-down method: the power supply is small in size, heavy in weight, and the power efficiency is very low, 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, and the power efficiency is relatively high. Generally, it can achieve 70% to 80%, and it is also widely used. 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 abnormal load has poor adaptability.

(6) PWM control mode switching power supply: It is mainly composed of four parts: input rectification filtering part, output rectification filtering part, PWM voltage stabilization control part, and switching energy conversion part. The basic working principle of PWM switching regulator is that under the condition of input voltage, internal parameters and external load changes, the control circuit performs closed-loop feedback through the difference between the controlled signal and the reference signal, and adjusts the pulse width of the main circuit switching device. Make the output voltage or current of the switching power supply stable (that is, the corresponding regulated power supply or constant current power supply). The efficiency of the power supply is extremely high, generally 80% to 90%, and the output voltage and current are stable. Generally, this kind of circuit has perfect protection measures and belongs to high reliability power supply.