- on Power Supplies
- Published in issue 7/2009 on page 22
Low-drop Series Regulator using a TL431
A simple way of charging 12 V lead-acid batteries is to hook up a small unregulated 15 V 'wall wart' power supply. This can easily lead to overcharging, though, because the off-load voltage is really too high. The remedy is a small but precise series regulator using just six components, which is connected directly between the power pack and the battery and doesn't need any heatsink.