Tired of using huge batteries in embedded design? Well Guy from Spritesmod managed to power AVR microcontroller from single AA battery with simple circuitry which is driven by AVR microcontroller itself. As industrial devices uses DC-DC converters to rise voltages like from 1.5V to 5V and so on, there is same principal used as well, just DC-DC converter control is done bu AVR MCU itself.
He didn’t use dedicated PWM control chip, but managed to drive converter with PWM generated with Attiny13 this way occupying one timer for this. Here is this fancy circuit. Of course to before MCU can generate control signal it has to start, for this there is starter button used, which rises voltage for short time to suitable when pushed. Then microcontroller starts and continues powering itself. With MOSFET switch efficiency of circuit reaches up to 73 percent. Main advantages of such powering method are low part count, soft poer off. But in other hand efficiency is still quite low and there is timer and one MCU pin occupied.