A gate driver is a power amplifier that accepts a low-power input from a controller IC and produces a high-current drive input for the gate of a high-power transistor such as an IGBT or power MOSFET. Gate drivers can be provided either on-chip or as a discrete module. The driver circuit is designed around three MOSFET for three different LED (RED, GREEN and BLUE). Arduino pin 5, 6 and 9 is connected to these three MOSFET gate as shown in circuit diagram. Three individual resistors each of 5.6K ground the gate pin of all these MOSFET. A dimming driver designed to drive an external n-channel MOSFET in series with the LED string provides wide-range dimming control up to 20kHz. In addition to PWM dimming, the MAX16834 provides analog dimming using a DC input at REFI.
Switching regulators, aka 'DC-to-DC', 'buck' or 'boost' converters, are the fancy way to power an LED. they do it all, but they are pricey. what is it they 'do' exactly? the switching regulator can either step-down ('buck') or step-up ('boost') the power supply input voltage to the exact voltage needed to power the LED's. unlike a resistor it constantly monitors the LED current and adapts to keep it constant. It does all this with 80-95% power efficiency, no matter how much the step-down or step-up is.
Pros:
- consistent LED performance for a wide range of LED's and power supply
- high efficiency, usually 80-90% for boost converters and 90-95% for buck converters
- can power LED's from both lower or higher voltage supplies (step-up or step-down)
- some units can adjust LED brightness
- packaged units designed for power-LED's are available & easy to use
Cons:
- complex and expensive: typically about $20 for a packaged unit.
- making your own requires several parts and electrical engineering skillz.
One off-the-shelf device designed specially for power-led's is the Buckpuck from LED Dynamics. I used one of these in my power-led headlamp project and was quite happy with it. these devices are available from most of the LED web stores.