LED drive power is the power supply is converted to a specific voltage and current to drive the LED light voltage converter is usually the case: the input of the LED drive power high-voltage power frequency AC (City), low voltage DC high voltage direct current, low voltage high frequency AC (eg, electronic transformer output). LED driver power supply output voltage can be changed with the change of the LED forward voltage drop value constant current source.
According to the rules of grid electricity and LED driver power characteristics requirements, selection and design of LED drive power to take into account the following points:
A high reliability, especially as the drive power of the LED lights installed in the high-altitude, inconvenient repairs and maintenance spend.
(2) high-efficiency LED energy-saving products, the higher the efficiency of the drive power. For the power to install the LED drive power lighting within the structure, is particularly important. LED luminous efficiency of LED temperature decreases, so the led 1w heat dissipation is very important. High efficiency power supply, the loss power, heat lamps, and reduces the temperature rise of the lamps. Beneficial to delay the LED light failure.
3 high power factor power factor power grid load requirements. Appliances generally less than 70 watts, there is no mandatory targets. Power is not a single electrical power factor on the grid has little effect, but at night we light a lamp, focus too much on similar load, the grid will produce a more serious pollution. 30 watts to 40 watts of LED drive power, said that in the near future, will power factors may have certain specifications.
4-driven approach is now common, there are two: one is a constant voltage source for the constant current source, each constant current source separately to each LED power supply. In this way, the combination of flexible, all the way to the LED fault, does not affect the other LED's work, but the cost will be slightly higher. Another is a direct constant current power supply, led power 10w in series or parallel operation. Its advantage is low cost, but the flexibility is poor, but also to solve a LED fault, does not affect other LED running. These two forms co-exist within a certain period of time. Multi-channel constant-current output power supply, in terms of cost and performance. May be a future direction of the mainstream.
Surge Protection LED Surge capacity is relatively poor, especially the anti-reverse voltage capability. Is also important to strengthen this protection. Some LED lights installed in the outdoors, such as LED street lights. Kai rejection grid load and the induction of lightning from the grid system will invade a variety of surge, some surge can cause damage to the LED. LED driver power supply have to inhibit the intrusion of the surge, the ability to protect the LED is not damaged.
Protection features Power In addition to the normal protective function, the best increase in the constant current output LED temperature negative feedback to prevent the LED temperature is too high.
7 protection aspects of lighting outside mount type, the power structure should be waterproof, moisture, shells and light fastness.
8 drive power of life and the life of the LED adapter.
9 To meet safety and electromagnetic compatibility requirements.
With the increasingly widespread application of LED, the led 10w drive power performance will be more and more suited to the requirements of the LED.
1, according to driving methods can be divided into two categories:
(1) constant-current type:
a constant current drive circuit output current is constant, and the output DC voltage with the change of the load resistance of different sizes within a certain range, the load resistance small, the output voltage, load resistance the greater the output voltage will be higher;
b, the constant current circuit are not afraid of the load short-circuit, but it is prohibited to load completely open.
c, the constant current drive circuit driving the LED is an ideal, but the relatively higher prices.
d should be noted that the Maximum current and voltage values, it limits the number of LED use;
(2) The regulator type:
, when the parameters identified in the regulator circuit, the output voltage is fixed, and the output current changes with the changes in load;
b, the voltage regulator circuit are not afraid of the load open, but it is prohibited to load completely short-circuit.
c, the regulator drive circuit drive led power 50w , each string with a suitable resistor before each string of LED display brightness average;
d, brightness will be affected by the rectifier from the voltage change.
2, the circuit structure classification
(1) Resistance capacitor step-down way: through a capacitor step-down in the use of the flashing, the role of the charge and discharge, the instantaneous current through the High Power LED 50W great, easy to damage the chip. Vulnerable to fluctuations in grid voltage, power efficiency, low reliability.
(2) resistance buck: through resistance buck, by the interference of the power grid voltage variations, are likely to cause the power supply dropping resistor to consume much energy, so this power supply power supply efficiency low, and reliability of the systems are relatively low.
(3) conventional transformer step-down way: power, small size, weight, emphasis on power efficiency is very low, generally only 45% to 60%, so rarely used, reliability is not high.
(4) electronic transformer step-down mode: low power efficiency, voltage range is not wide, generally 180 ~ 240V, corrugated interference.
(5) the RCC buck mode switching power supply: voltage range is wide, relatively high power efficiency, the general can do 70% to 80%, the applications are wider. Since the oscillation frequency of this control is not continuous, the switching frequency is not easy to control the load voltage ripple coefficient is relatively large, abnormal load and poor adaptability.
(6) PWM control mode switching power supply: mainly consists of four parts, part of the input rectifier filter, the filter portion of the output rectifier, PWM regulator control section, the switching energy conversion part. Basic working principle of the PWM switching regulator is the case of changes in input voltage, the internal parameters and external load, the control circuit through the control signal and reference signal difference between the closed-loop feedback, adjust the pulse width of the main circuit switching device turns on. makes the switching power supply output voltage or current stable (ie, the corresponding power supply or constant current power supply). High power efficiency, the general can do 80% to 90%, output voltage and current stability. General this circuit has the perfect protection measures, is a highly reliable power supply.