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High-power LEDs typically operate at low voltages - usually 3 to 4 Volts - and operate most efficiently when they are driven by direct current (DC) – usually 0.35 to 2Amps. Since many lighting systems get their power via an alternating current (AC) source, LED lighting solutions must include special circuits to convert the input power to the direct current, low voltage needed by the LED subsystem. Efficient, well-engineered driving circuits are critical to LED lighting performance, reliability and cost.
Your choice of LED will determine the maximum forward current that can be applied to the LED subsystem. Driving the LED at its maximum forward current will result in the maximum light output and may reduce the number of LEDs needed to meet your illumination requirement; lowering the cost of the system. However, the higher the current, the less efficient (lumens/Watt) the system will be; possibly increasing the cost of the thermal management system and definitely increasing the cost of system operation. The fact that drivers with higher current capability are sometimes more expensive solutions must also be figured into the cost trade-off.
Once the current level is chosen, there are still a number of driver options that will affect cost, efficiency, space and thermal management requirements. For example, a linear-type driver is very inexpensive, but can be very inefficient and may possibly add to the system's thermal issues. On the other hand, a switching-type driver is more efficient, but more complex and expensive.
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