Classified by circuit structure
(1) Resistor and capacitor step-down method: step-down by capacitor, during flash use, due to the effect of charging and discharging, the instantaneous current through the LED is extremely large, which is easy to damage the chip. It is susceptible to the influence of power grid voltage fluctuations, and the power supply has low efficiency and low reliability.
(2) Resistor step-down method: The resistance step-down method is greatly affected by changes in 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 power supply method is very low. , And the reliability of the system is 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 generally rarely used and has low reliability.
(4) Electronic transformer step-down method: the power supply efficiency is low, 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% to 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 also relatively large, and the adaptability to abnormal loads is poor.
(6) PWM control mode switching power supply: 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 when the input voltage, internal parameters and external load 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. 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 power supply efficiency is extremely high, generally 80% to 90% can be achieved, and the output voltage and current are stable. Generally, this kind of circuit has perfect protection measures, which is a high-reliability power supply.
