A power supply, led fluorescent bulb can be classified into two categories:
A. constant current:
1, constant current driver circuit drive LED is ideal. The shortcoming is that the price is higher.
2, the constant current circuit though not afraid load short circuit, but it is strictly prohibited to load completely open.
3, constant current driving circuit of the output current is constant, and output of the dc voltage but with the size of the load resistance of difference within a certain range change.
4, to limit the use of LED the number, because it has the largest under current and voltage.
B. voltage is stabilizing type:
1, the parameters determined voltage circuit, the output voltage is fixed, the output current is of the number and the load changes.
2, though not afraid open load voltage circuit, but it is strictly forbidden to load completely short circuit.
3, rectifier voltage change will affect the LED brightness.
4, to make each string voltage to the circuit driver LED display brightness level, the need to add appropriate resistance canbe .
Second, LED by power supply circuit structure can be divided into six types:
1, conventional transformer book:
The advantages of this power source are small, the deficiency of lay particular stress on, power efficiency is weight is low, generally in 45% ~ 60%, and for reliability are not high, so general seldom use.
2, electronic transformer book:
This power source structural deficiency is conversion efficiency is minimal, the voltage narrow range, general 180 ~ 240 V, corrugated interference.
3, capacitance book:
This kind of led fluorescent bulb replacement to the influence of the voltage fluctuation, the efficiency is low, should not be used in LED flashing, because circuit through the capacitance step-down, use in flashing, due to the role of the charging and discharging, LED by the instantaneous electric current is great, easy to damage the chip.
4, resistance book:
This power supply mode power supply is very inefficient, and reliable system is correspondingly lower. Because circuit through the resistance step-down, by the network voltage change of interference is bigger, not easy to make stabilized voltage power supply, and step-down resistance itself will consume much of the energy.
5, RCC step-down type switch power supply:
The way the power supply voltage LED advantage is more varied range, the efficiency is higher, can generally be between 70% and 80%, and the wider application. The disadvantage is mainly switch frequency not easy to control, the load voltage ripple coefficient is bigger, the abnormal situation flexible load.
6, PWM control type switch power supply:
For now, PWM control mode of the power supply is dled fluorescent bulbs an ideal, because this kind of switch power supply output voltage or current is exceptionally stable. Power conversion efficiency is extremely high, commonly can be as high as 80% ~ 90%, and the output voltage, electric current is stable. This way LED power chiefly consists of four parts they were: input rectifier filter part, the output voltage of PWM rectifier filter, the control part, switch energy conversion parts. And this circuit has perfect protection measures, belong to high reliability power supply.