In order to save energy and energy, LED has been a great implementation, but the LED are
required to have a power supply drive, its good or bad will directly affect the LED life,
and thus how to do a LED driver power is the focus of the LED power source weight. This
paper analyzes some of the LED drive power problems, hoping to provide some assistance to
the engineers.
1, the drive circuit directly affects LED life
We said that the LED driver, including digital-driven and analog push-driven two, digital-
driven index word circuit driver, including digital dimming control, RGB full color changes
and so on. Analog push refers to the analog circuit driver, including AC constant current
switching power supply, DC constant current control circuit. The drive circuit consists of
electronic components, including semiconductor components, resistors, capacitors,
inductors, etc., these components have the use of life, any failure of a device will cause
the failure of the entire circuit may be some function failure. LED use of life is 5-10
million hours, according to 50,000 hours count, a series of light, nearly 6 years of life.
Switching power supply life is difficult to reach 6 years, the market to sell the switching
power supply warranty period is usually 2-3 years to reach 6 years warranty power supply is
military grade, the price is usually 4-6 times the power supply, usually The lighting
factory is very difficult to bear. So LED lighting problems for the drive circuit problems.
2, heat problems
LED for the cold light source, operating junction temperature can not exceed the limit, the
description will have to leave the remaining margin. The design of the entire lamp to
consider the appearance of beautiful, easy to install, with light, heat and many other
problems, to find a balance in many elements, so that all the lamps is the best.LED lamps
are not long to develop The experience is not much, many depictions are constantly perfect.
Some LED lighting manufacturers use power for outsourced perhaps outsourced, lamp depicts
the power to know little, to the LED cooling space larger, to the power of the cooling
space smaller. Usually painted after the light and then find the appropriate power supply
to match, so give the power supply to bring a certain degree of difficulty. Often
encountered due to the smaller interior space of the lamp may be higher internal
temperature, and the cost of manipulation is low, can not be equipped with the appropriate
power. Some LED lighting factory has power development talent, in the beginning to describe
the early evaluation of the lamp, the power of the description of the synchronization, will
be able to deal with the above problems. In the description of the LED to sum up the heat
and power of the heat, all control the temperature rise of lamps, so that the ability to
draw a better lamp.
3, the power to describe the problem
A, power depiction. Although the LED light efficiency, but there are 80-85% of the heat
loss, resulting in 20-30 degrees inside the lamp temperature rise, if the room temperature
of 25 degrees, the lamp has 45-55 degrees, the power supply for a long time in high
temperature environment Under the operation, to ensure that life must increase the power
margin, usually left to 1.5-2 times the margin.
B, component selection. Lamp internal temperature 45-55 degrees situation, the internal
temperature rise is still about 20 degrees, then the component adjacent to the temperature
to reach 65-75 degrees. Some components in the high temperature conditions will drift
parameters, and some life will be shortened, so the equipment to be selected at a higher
temperature for a long time to use, pay special attention to electrolytic capacitors and
wires.
C, electrical function drawing. Switching power supply parameters of the LED alignment,
mainly constant current parameters, the size of the resolution of the brightness of the
LED, if the bulk current error is large, the brightness of the entire batch of light is not
uniform. And the temperature change can also cause the power supply output current offset.
Usually within the volume error control within +/- 5%, to ensure that the brightness of the
lamp common. LED forward voltage drop error, the power to describe the constant current
voltage scale to include the LED voltage scale. Multiple LED series using the time
division, the minimum voltage drop multiplied by the serial number for the lower limit
voltage, the maximum voltage drop multiplied by the serial number for the upper limit
voltage, the power supply constant current voltage scale slightly wider than this, usually
the upper and lower limits of the Stay 1-2V margin.
D, PCB layout .LED lamps left to the power of the smaller scale (unless the power is
external), so the PCB design on the higher demand, to think more elements. The safety
interval to stay enough, the demand input and output barrier power supply, the primary
circuit and the secondary side of the circuit requires voltage 1500-2000VAC, PCB at least
enough to stay 3MM interval. If the metal shell of the lamp, the entire power supply board
also think about some of the high pressure and the safety of the shell interval. If there
is no room to ensure that the safety interval conditions will use other methods to ensure
insulation, such as punching on the PCB, plus insulation paper, potting insulation, and so
on. Other cloth also think about heat balance, heating elements to be evenly distributed,
can not be set to prevent some of the temperature rise. Electrolytic capacitors away from
heat, slow aging, extending the use of longevity.
E, certification problems. At present, China has not yet aligned with the norms of LED
lamps, the relevant part of the country is being developed, the domestic sales of lamps and
lanterns is a reference to the norms of lighting, export CE or UL certification is done,
and some reference to foreign LED lighting specifications to do The So the alignment of
this situation, the description of switching power supply to be satisfied with the above
specifications are more difficult, we can only match the different needs of different
certification is not the same.
4, the use of parameters.
Outsourcing power supply in the selection of the main constant current and constant current
voltage scale. The constant current value is selected as the specification of the LED
current drop. Voltage scale selection should be moderate, try not to choose a larger scale,
to prevent the power of the spoil
LED drive power supply common problems |
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