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Light-emitting diodes (LEDs) are the next-generation lighting components used in buildings and indoor lighting. They are much more efficient than incandescent lamps. However, they must be driven by dedicated electronic circuits to ensure they are not subject to excessive stress. The long life claimed in the product specifications. For this technical premise, this article will explore how to use simple LED driver circuits to provide the necessary reliability and minimize the cost of the fixture.
LED characteristics and indoor lighting design are more efficient LED lighting features have enabled interior lighting designers to further design new lighting solutions. For example, LEDs are small in size and can be densely arranged to allow them to be placed in flexible lighting strips. Inside, or easy to hide in the cabinets and stairs, to achieve more design flexibility. In addition, the main operating parameters of the LED are relatively simple, as long as the current is kept constant and lower than the maximum current that can be withstand, further working within the design parameters without suffering from excessive stress, the LED life will be one hundred times longer than the incandescent bulb. Become another key advantage. Therefore, if the drive circuit meets the LED specifications, the output of the light source will remain constant, and the service life can exceed 50,000 hours.
On the other hand, the design guidelines for buildings and indoor lighting fixtures must be globally compliant, and their luminaires must operate at a frequency of 50 or 60 Hz over a full range of universal voltage specifications of 85 to 265 VAC. The power supply circuit covering this universal voltage requirement has been designed and is in production, and it is expected to further penetrate the computer and mobile phone market based on this design in the future. It must be noted that these power supply designs are optimized for the end product, but are not necessarily the best solution for the LED drive circuit.
Lighten the design burden and keep the current constant. Since the traditional power supply provides accurate voltage output and different current levels, a resistor can be connected to the LED to limit the current. A prerequisite for such a design is to clearly know the voltage across the LED (string) and this voltage will not change as the LED temperature changes. Disadvantageously, the LED forward voltage typically varies with temperature, so LED manufacturers must encode their components based on forward voltage, allowing luminaire manufacturers to build luminaires that match the LED forward voltage at a fixed temperature. design.
With this design consideration, circuits that do not require LED coding are more attractive because they save LED manufacturers time and produce LEDs that are cheaper. Not only that, because of the safety problem, the LED forward voltage also has a negative temperature coefficient (that is, the forward voltage drops when the temperature rises), which may cause the circuit to overheat and lose control. Therefore, the designer must also require the designer to construct the protection circuit, which is also a Pen extra cost.
Therefore, the best solution for the LED drive circuit is to monitor the current and keep the current constant. This type of circuit is not affected by the LED forward voltage, does not require LED coding, and eliminates the effect of the LED on the negative temperature coefficient of the forward voltage. In addition, such circuits can be used in a wide range of applications, from complex switching regulators to linear regulators with feedback loops, while complex switching regulators are ideal for high-light output applications such as street lighting with luminous efficacy.
It can be seen that both buildings and indoor lighting fixtures are suitable for simple, economical and rugged hybrid circuit design. Although their performance requirements may not be as high as complex switching regulators, the low cost and simple design architecture make them extremely polar. Attractive choice.