Skills: LED driver power supply planning summary of the four major questions
LED driver power supply quality is good or bad will directly affect the LED life. Therefore, how to do a good job a LED driving power supply is led power supply planners in weight.
In the present day, in order to save energy, LED has been great implementation, but the LED needs to have a power driven, its quality will directly affect the LED's life. Therefore, how to do a good job a LED driving power supply is led power supply planners in weight. This article describes some of the LED drive power of doubt, hoping to provide a little help to the engineer.
1, the driving circuit directly affects the LED of life
We're talking about the LED driver includes a digital drive and imitate drive, digital drive of the driver that the digital circuit, including digital adjustable optical manipulation, RGB color changes. The driving circuit is driven by an analog driver, which comprises a AC constant current switching power supply and a DC constant current control circuit. Driving circuit composed of electronic components, including a semiconductor element, resistors, capacitors, inductors, and so on, these elements have with thelife and any equipment failure will cause the failure of circuit may partly function failure.
LED is using his 5-10 million hours, at 50 thousand hours, a series of light, there are nearly 6 years of life. Number of switching power supply is very difficult to reach 6 years, market * * of the switching power supply of the warranty period is usually 2-3 years, reaching 6 years warranty power is military rank, the quotation is 4-6 times normal power supply, usually of lamps and lanterns factory is very difficult to accept. So the problem of LED lamps and lanterns for the driver circuit problems.
2, heat doubt
LED for the cold light source, operating junction temperature can not exceed the limit, planning to leave a certain margin. All the lamps and lanterns of planning to think about the beautiful shape, convenient device, light distribution and heat dissipation many questions to seeking for the balance point in the many elements, so all the lamps and lanterns is the best LED lighting development time is not long, capable of learning the experience is not much, many planning is continuous improvement. Power used in some LED lamp manufacturers outsourcing may be purchased, lamps and lanterns planners to power understanding not much, to LED thermal dissipation space is larger, to power of less space for heat dissipation.
Usually planning a good lighting and then find a suitable power supply to matching, so that the power supply will bring a certain degree of difficulty. Often encountered due to the interior space of the lighting fixture is smaller, the internal temperature is higher, and the cost control is low, can not be equipped with suitable power supply. Some LED lamps and lanterns plant has the power supply development ability, in the beginning of planning lighting evaluation, the power supply planning synchronization, you can handle the above questions. In the planning to sum up thinking about LED of heat and power dissipation, all the control of the temperature rise, so that the ability to plan a better lighting.
3, the power of the planning questions
A, power planning. Although the LED with high light efficiency, but also 80-85% of heat loss, resulting in the ascending temperature 20-30 degrees $10.6626 inside the lamp, if room temperature 25 degrees in, inside the lamp is 45-55 degrees, the power supply for a long time under the environment of high temperature operation, to ensure the life is must increase the margin of power, usually reserved to 1.5-2 times the margin.
B, component selection. Lamp internal temperature 45-55 degrees, the internal temperature rise is about 20 degrees, the component adjacent to the temperature to reach 65-75 degrees. Some elements in the state of high temperature parameters will drift, some days will be shortened, so the equipment should be selected to be used in high temperature for a long time, with particular attention to the electrolytic capacitors and conductors.
C, electrical function planning. Switching power supply for parametric programming led, mainly is the constant flow parameters, the current size decision led brightness, if batch current error is larger, the entire batch of lamp brightness uneven. And temperature changes can also cause the power output current offset. Is usually a lot of error control in the +/-5%, to ensure that the brightness of the lamp common.LED forward voltage drop error, power supply planning constant current voltage scale to include the LED voltage scale.
A plurality of LED series using time, minimum pressure drop is multiplied by the series number for lower voltage, the maximum pressure drop multiplied by the serial number for upper limit voltage, power supply constant current voltage scale to than the scale slightly wide, usually limit the left margin of 1-2V.
D, PCB layout planning, LED lamps and lanterns left power on a small scale (unless an external power supply), so a higher demand on the PCB layouts to the elements of thinking too much. Security interval to be left enough, the need to input and output blocking power supply, once the side circuit and the two side circuit needs to withstand voltage PCB, at least on the 1500-2000VAC to stay enough 3MM intervals. If the lamp is the metal shell, all the power of the board but also on the safety of high voltage part and an interval.
If there is no space to ensure safe interval under the condition to use another way to ensure insulation, such as punch a hole on the PCB, and insulating paper, potting insulating glue. The other plate also thinking of heat balance, the heating element should be evenly distributed, not have placed, prevent local temperature increase. The electrolytic capacitor away from heat, slow aging, extend the life.
E, certification questions. Currently no specification for LED lamp, part of the state is to study the formulation and certification of domestic sale of lamps and lanterns is refer to the specification of lighting lamps and lanterns, the export is CE or UL certification, also some reference foreign LED lamps specification to do. So for this situation, the switching power supply planning to be satisfied with the above specifications are more difficult, we can only do not meet the requirements of the same kind of certification.
4, the use of parameters
Purchased power mainly depends on voltage scale constant flow and constant flow in the selection. The constant current value is selected as the LED of the current bias of the specification. Voltage scale selection should be moderate, as far as possible not to select a larger scale, prevent