See USB 5V to 1.5V/3V Step Down Converter Circuit using LM317. With this, we can use MP3 players (requires only 1.5V AA battery) with USB(5V).
Small appliances have microcomputer that requires 5V power supply. Why it can use only 1.5V battery? The 1.5V to 5V boost converter circuit inside them.
No light! because of a low voltage battery. How do you increase the voltage up? You can do many ways. And, I recommend a simple step-up converter circuit using TDA2822.
I like the 12V LED. But I have only 3V of batteries. So, No light. When using this circuit, I can get light of the LED at 100 mA. And, an adjustable output voltage.