Buck-Boost LED Driver
Created: Sep 01, 2014
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A Light Emitting Diode (LED) is a semiconductor device that emits lights when energized. LEDs have emerged in recent years as viable sources of light. They are no longer used solely as 'status light' indicators for electronic equipment. Advances in technology have provided LEDs that are typically 3 times more efficient than incandescent bulbs. LEDs are also extremely durable and have lifetimes exceeding tens of thousands of hours.
The buck-boost converter is used when the supply voltage may be above or below the required output voltage. The buck-boost converter is especially useful for battery applications. The buck-boost topology is also known as a flyback or inverting regulator.
The PIC16F785 makes a great choice for this application because it combines a MCU with many on-chip analog peripherals. The on-chip op amp of PIC16F785 is used to amplify the voltage across the current sensing resistor. This allows a much smaller sensing resistor to be used and reduces power dissipation. The PIC16HV785 device can be used to eliminate the requirement for an external 5V regulator when operating from higher supply voltages. This application has unused analog resources which could be used to control another LED driver, power supply, or battery charging circuit.