(1) Constant formula:
a, constant current output driver circuit is constant, while the output DC voltage but with the load resistance of different sizes vary within a certain range, the load resistance is small, the output voltage is low, the greater the load resistance, output the higher voltage;
b, constant load short circuit is not afraid, but non-load completely open.
c, constant current drive circuit drives the LED is an ideal, but the relatively high price.
d, should pay attention to withstand the maximum current and voltage values to use, it limits the number of LED's use;
(2) Regulators formula:
a, after regulator circuit when the determined parameters, the output voltage is fixed, but with the current output and the increase or decrease in the load change;
b, voltage regulator circuit is not afraid of open load, but the load is completely non-short-circuiting.
c, to the regulator drive circuit drives LED, each string need only add an appropriate resistor so that each string of LED display brightness average;
d, the brightness will be affected by changes in the voltage from the rectifier.
Press the circuit configuration
(1) resistor, capacitor step-down mode: down through the capacitor, when using flash, due to the effect of charge and discharge, the instantaneous current through the LED is great, easy to damage the chip. Vulnerable to fluctuations in grid voltage, power efficiency, low reliability.
(2) Resistance Buck ways: through resistance voltage, interference from the grid voltage variation is larger, is not likely to cause the power supply, the dropping resistor to consume much of the energy, so that low power efficiency power supply and the reliability of the system are relatively low.