小说,好看的玄幻小说

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

　　(1) Constant current type

　　a. The output current of the constant current drive circuit is stable, but the output DC voltage changes in a certain scale with the size of the load resistance. If the load resistance is small, the output voltage will be low. The larger the load resistance is, the higher the output voltage will be;

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

　　c. The constant current driving circuit is ideal to drive LED, but the price is relatively high.

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

　　(2) Stabilized voltage type

　　a. When the parameters of the voltage stabilizing circuit are determined, the output voltage is fixed, while the output current changes with the increase or decrease of the load;

　　b. The voltage stabilizing circuit is not afraid of load open circuit, but it is strictly prohibited to short circuit the load completely.

　　c. The LED is driven by a voltage stabilizing driving circuit, and each string needs to be added with a proper resistance to make each string of LED display brightness uniform;

　　d. The brightness will be affected by the voltage change from the rectifier.

　　2. Classification by circuit structure method

　　(1) Resistance and capacitance step-down method: after capacitance step-down, due to the role of charge and discharge, the instantaneous current through LED is very large, and the chip is simply damaged. It is easy to be affected by the voltage fluctuation of the power grid, with low power supply and low reliability.

　　(2) Resistance step-down method: after resistance step-down, the disturbance caused by the change of grid voltage is large. It is not simple to make a stabilized voltage power supply. The step-down resistance consumes a lot of energy, so the power supply of this power supply method is very low, and the reliability of the system is also low.

　　(3) Conventional transformer step-down method: the power supply is small in size, heavy in component, low in power, only 45% - 60% in general, so it is seldom used and its reliability is not high.

　　(4) Electronic transformer step-down method: the power supply is low, the voltage scale is not wide, generally 180-240v, ripple disturbance is large.

　　(5) RCC voltage reduction method switching power supply: the voltage stabilization scale is relatively wide, the power supply is relatively high, generally can achieve 70% ～ 80%, and is widely used. Because the oscillation frequency of this control method is not connected, the switching frequency is not easy to operate, the ripple coefficient of load voltage is relatively large, and the adaptability of abnormal load is poor.

　　(6) PWM control method switching power supply: mainly consists of four parts, input rectifier filter part, output rectifier filter part, PWM stabilized voltage control part, switch energy conversion part. The basic working principle of PWM switch voltage stabilization is that when the input voltage, internal parameters and external load are changed, the control circuit reacts in a closed loop through the difference between the controlled signal and the reference signal, regulates the pulse width of the main circuit switching device, and makes the output voltage or current of the switching power supply stable (i.e. the corresponding regulated power supply or constant current power supply). The power of the power supply is very high, generally it can achieve 80% - 90%, and the output voltage and current are stable. Generally, this kind of circuit has perfect protection measures and belongs to high reliable power supply.

　　Article source: Jiangmen led waterproof power supply manufacturer http://www.賽亞光電.com

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