(1) Step-down method of resistance and capacitance: When the capacitor is stepped down, when flashing, the instantaneous current through the LED is extremely large due to the charge and discharge effect, which easily damages the chip. Susceptible to the influence of power grid voltage fluctuations, the power supply has low 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 this power supply method has low power efficiency , 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 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: mainly consists of four parts, the input rectification filter part, the output rectification filter part, the PWM voltage stabilization control part, and the 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.
Classification of power installation positions
The driving power can be divided into external power and built-in power according to the installation position.
(1) External power supply
As the name implies, an external power supply is an external power supply. Generally, the voltage is relatively high, and if it is dangerous to people, an external power supply is required. The difference from the built-in power supply is that the power supply has a shell, and there are common street lights.
(2) Built-in power supply
That is to install the power supply in the lamp, generally the voltage is relatively low, 12v to 24v, there is no hidden danger to people. This common one is a bulb lamp.