With the rapid development of the LED, it was quickly applied to the field of long-term environment occupied by incandescent and fluorescent lighting, and even vehicle equipment. For high-power LED power supply, the best way is the current source. Because the vast majority of energy, including batteries, generators and industrial trunk voltage source, there is little current source. So they need to be inserted in the middle of the LED and power supply circuit. The best choice is a high efficiency current source with a voltage feedback. The LED current is greater than 0.35A, the inductive relay is usually the best choice.

Derived from a series of circuits, based on a single power IC relay in order to achieve the goal of high efficiency and miniaturization. Circuit designers by reducing the use of larger components, such as external transistors, switches, large-capacity capacitor and current limiting resistor, etc., and as much as possible in the circumstances to maintain the normal operation of the high brightness of the light passing to the farther the better to to achieve the goal of efficiency and miniaturization.

The high frequency switching regulator to the basic adjustment of the LED circuitry. Input voltage range of 3.6V to 6.5V, can provide up to 1A of current to drive LEDs, and a current sense resistor to control current regulator closed-loop.
   
The designers of these circuits have the same concept in the design: a complete single-mode integrated circuit relays and micro-power op amp. The op amp final 1.25V feedback to the IC. Although the nodes are to the standard voltage topology as the goal, but the op amp can make it with a weak current is sensitive to voltage and slightly different current topology to match. All of these circuits do not need an external power switch. This design to go in addition to the usually large filter capacitor in the switching power supply near the high frequency harmonics of the LED current, because there is no need smoothing. The most popular choice of all circuits in the op amp's input into the adjustable bias, relying on IC via a resistor and an adjustment by the internal potentiometer to increase the brightness adjustment.