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Common problems and solutions in LED power supply design

Author : Shenzhen Crown Lighting

Update time : 2021-06-22 20:55:45

Common problems and solutions in LED power supply design

In the current life, in order to save energy and electricity, led lighting technology has been greatly promoted, but LED lights need to have a power driver, and its quality will directly affect the life of the LED light, so how to make a LED driver is the LED power designer's top priority.

1. The driving circuit directly affects the life span
What we call lighting LED driver includes digital driver and analog driver. Digital driver refers to digital circuit driver, including digital dimming control, RGB full-color change and so on. Analog drive refers to analog circuit drive, including AC constant current switching power supply and DC constant current control circuit. The drive circuit is composed of electronic components, including semiconductor components, resistors, capacitors, inductances, etc. These components have a service life, and the failure of any one device will lead to the failure of the entire circuit or partial functional failure.

2. Heat dissipation issues
LED is a cold light source, the working junction temperature cannot exceed the limit, and a certain margin should be left in the design. The design of the entire led luminaire should consider many issues such as beautiful appearance, convenient installation, light distribution, heat dissipation and so on. It is necessary to find a balance among many factors, so that the overall luminaire led effect is the best.

Some LED lighting designers don't know much about power supplies, and the space for heat dissipation for led luminaire lighting is large, and the space for heat dissipation for power supply is small. Generally, after designing the luminaire lamp, we need to find a suitable power supply to match, which brings a certain degree of difficulty to the matching of the power supply. It is often encountered because the internal space of the lighting luminaires is small so the internal temperature is high. It cannot be equipped with a suitable power supply.

In the design, it is necessary to comprehensively consider the heat dissipation of the lighting luminaire and the power supply, and control the temperature rise of the lamp led as a whole, so that a better lamp can be designed.

3. Problems in power supply design
A. Power design.
Although the LED has high luminous efficiency, there is still 80-85% of heat loss, resulting in a temperature rise of 20-30% ($10.6626) degrees inside the luminaire lamps. If the room temperature is 25 degrees, there will be 45-55 degrees inside the lighting led lamp, and the power supply is long. When working in a high temperature environment, the power margin must be increased to ensure the service life, and generally leave a margin of 1.5-2 times.

B. Component selection.
When the internal temperature of the lamp is 45-55 degrees, and the internal temperature rise of the power supply is about 20 degrees, the temperature of the component accessories should reach 65-75 degrees. Some components will shift their parameters at high temperatures, and some will shorten their lifespan. Therefore, components should be selected that can be used for a long time at a higher temperature, paying special attention to electrolytic capacitors and wires.

C. Electrical performance design.
The switching power supply is designed for LED parameters, mainly constant current parameters. The size of the current determines the brightness of the LED light. If the batch current error is large, the brightness of the entire batch of lights will be uneven. Moreover, changes in temperature can also shift the output current of the power supply. Generally, the batch error is controlled within ±5% to ensure the brightness of the led lamp is consistent. The forward voltage drop of the LED has deviation, and the constant current voltage range of the power supply design should include the voltage range of the LED lights.

D. PCB layout design.
The size of the LED lamps reserved for the power supply is small (unless the power supply is external), so the PCB design requirements are higher. The safety distance must be sufficient, and the power supply that requires input and output isolation, the primary side circuit and the secondary side circuit require a withstand voltage of 1500-2000VAC, and at least a sufficient distance of 3mm on the PCB. If there is no space to ensure a safe distance, other measures must be used to ensure insulation, such as punching holes in the PCB, adding insulating paper, and potting insulating glue. In addition, the layout of the board should also consider the heat balance, and the heating elements should be evenly distributed and cannot be placed in a concentrated manner to avoid local temperature rise. The electrolytic capacitor is far away from the heat source to slow down the aging and prolong the service life.

E. Use parameters.
The choice of power supply mainly depends on the voltage range of constant current and constant current. The constant current value is chosen to be lower than the standard current of the LED light. The selection of the voltage range should be moderate, and try not to choose a larger range to avoid waste of power.

Our LED panel, downlights, solar flood light, solar LED Parking Lot Lighting, LED Tunnel Lights for Tunnel Lighting and LED High Bay Lamp are using branded led drivers, including Mean well, Lifud, Tridonic.

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