When designing LED lighting fixtures, it’s crucial to consider the appropriate LED driver power supply and the LED connection method. White LED lighting fixtures typically have a forward voltage range of 2.8-3.6V , a power rating of 1W or 3W, and an operating current of 350mA or 700mA (actual operating currents are 300mA or 600mA) .
To design an LED driver, it’s essential to understand the operating principles of LEDs. LED brightness is primarily a function of voltage and current . Small changes in voltage can cause large changes in current , and thus in LED brightness. To maintain optimal LED brightness, a constant current power supply is required. An LED driver is a power converter that outputs a constant current, not a constant voltage. In all cases, an LED driver must deliver a constant and stable current, and the ripple current must be kept within a certain range.
When selecting an LED driver, determine the LED voltage at operating temperature . Choose an appropriate driver output voltage (operating voltage) range based on the number of connected LEDs and their series/parallel connections.
The maximum LED operating voltage is calculated by multiplying the maximum LED voltage by the number of LEDs in series. This maximum operating voltage should be at least 5V less than the maximum output voltage of the power supply. The minimum LED operating voltage is calculated by multiplying the minimum LED voltage by the number of LEDs in series. This minimum operating voltage should be at least 5V higher than the minimum output voltage of the power supply. The total operating power of the LED driver is approximately 90% of the total power supply.