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  • Buck LED Driver Reference Design

  • Created: Sep 03, 2014

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Summary

This reference design shows a 1W or higher value LED that uses a minimum number of driver or controller. A buck topology switching power supply is the design theory that is being utilized in the circuit which uses an on-chip comparator in a PIC12F675 microcontroller. This design ensures an efficient transfer of power between the supply and the output. The microcontroller that is used in the design implements an intensity control, automated intensity compensation for low battery conditions, and has the ability to playback pre-programmed flash sequences.


The design focuses on two different high-power LED modules, a 1 watt and a 3 watt. The 1 watt module requires a typical drive of 3.4V at 350 mA to produce its full output brightness. The maximum current drive for the unit is 500 mA. Exceeding the maximum current specification for the module, even by short duration pulses, may result in damage. Therefore, the drive circuitry for the module must deliver a DC or mostly DC current to the LED module to produce a full brightness output. The drive requirements for the 3 watt module are similar, with full brightness output at 700 mA and a maximum current drive of 1A. The circuit described in this reference design delivers a mostly DC drive current with a small triangular ripple waveform superimposed at the drive level (VDRIVE). The triangular waveform is the result of the switching nature of the driver, and if kept small in relation to the DC drive current, will not exceed the instantaneous maximum current specification for the LED. In fact, the example designs have been designed with a safety margin to ensure that the instantaneous current delivered to the LED is always less than the maximum rating, even when delivering the full-rated current to the device.


The LED driver that uses buck topology design aims to use power efficiently between its supply and output that helps in reducing cost in building circuit. In addition, it contributes in reducing the power from a high source to a lower source component, like having an 18V laptop down to a 0.8V to 1.8V processor.

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