Whether high-power or low-power LEDs are used in lighting, they are generally composed of power supplies, LED drivers, LEDs, lenses and substrates. The key component is the LED driver, which must provide a constant current output to ensure that the LED emits The light will not flicker, and the LED color shift will not occur. The driver of the wind-solar hybrid LED street light generally accepts a DC voltage input of 24-48V.
The main design challenges for LED lighting applications include the following: heat dissipation, high efficiency, low cost, wide-range dimming without flicker, reliability, safety, and elimination of color casts. These challenges require a combination of appropriate driver circuit topology design and mechanical design to solve.
In LED lighting design, the biggest technical challenges will be high efficiency requirements, optical design, thermal management and improving the reliability of certain applications, such as LED street lights. In the application of LED lighting system, in addition to selecting suitable LED products, a complete LED lighting design also includes optical design, thermal design, product design and electrical drive design. In order to guarantee the advantages of LED lighting, LED driver circuits must be reliable, efficient, safe and low-cost. Therefore, for different LED lighting applications, it is first necessary to select the correct driver circuit topology.
Since LED lighting fixtures need to be composed of multiple LEDs, the discreteness of their parameters is also a technical problem. In addition to ensuring the consistency as much as possible through pre-selection and classification, a reasonable lamp structure (including the arrangement and position layout of the LEDs) and a suitable driving circuit must be designed to prevent the occasional energy concentration and damage to some LEDs. When only lighting lamps, parallel and series connection of LEDs cannot be avoided. As long as one LED is short-circuited or open during use, a small piece or the entire LED will be extinguished, affecting the lighting effect. Therefore, a simple and cheap protection circuit must be studied to minimize this adverse effect. In addition, due to the high requirements of LED on heat dissipation conditions, if the junction temperature of the LED exceeds the standard limit value, it will cause irreversible light intensity attenuation. Therefore, in addition to adequate heat dissipation measures, reasonable circuit design and circuit layout must also be considered when using, try to keep the LED in good working condition and give full play to its long life advantage. LED components For the application of LED in lighting, it is necessary to analyze its requirements from the perspective of the system. In general, LED lighting systems involve the following requirements:
(1) LED light source. The light source is compact and efficient, offering a wide range of colors and output power.
(2) Power conversion. Convert unstable battery power into DC constant current source to drive LED.
(3) Control and drive. The electronic circuit is used to control the constant current of the LED.
(4) Thermal management. To achieve longer operating life, temperature control is very important, and thermal design needs to be optimized.
(5) Optical devices. Focusing the light where it is needed requires the use of lenses or light guides.
These requirements are all important when developing high-efficiency LED lighting solutions. For LED drivers, the main challenge it faces is the nonlinearity of LEDs. This is mainly reflected in that the forward voltage of the LED will change with the change of current and temperature, the forward voltage of different LED devices will be different, the color rendering of the LED will drift with the change of current and temperature, and the LED must be in To achieve reliable operation within the range required by the specification, the main role of the LED driver is to limit the current within the range of operating conditions, regardless of changes in input conditions and forward voltage.