Most Canon Powershot cameras don't come bundled with a dc power plug. You can purchase separately a Canon ACK-DC10 AC Adapter or similar device for about $51 USD from either B&H Photo or Amazon. I wouldn't recommend buying one of the clones off eBay as they are really low quality.
Normally the ACK-DC10 is run off AC wall power.
If you want to power the camera off of a larger external battery for your timelapse, the ACK-DC10 has a female barrel power connector on the dummy battery. Make sure to provide a nominal 3.7 Volt DC power to the dummy battery module. This could be achieved with an adjustable linear voltage regulator.
Canon makes a few different wall power adapters for their different cameras:
- ACK-DC10 AC Adapter Kit for Powershot SD200, SD300, SD400 & SD450, SD780IS Digital Cameras
- ACK-DC30 AC Adapter Kit for Canon Powershot SD700, SD800, SD850, 880, & SD900 Digital Cameras
- ACK-DC20 AC Adapter Kit for Powershot S30, S40, S45, S50, S60, S70, S80, EOS Digital Rebel XT, XTi Digital Cameras.
- ACK-800 AC Adapter Kit for PowerShot A100, A200, A300, A310, A400, A510, A520 & A540 Digital Cameras
- ACK-DC40AC Adapter Kit for Canon PowerShot SD770 IS Digital Camera
- ACK-DC50AC Adapter Kit For Canon PowerShot G11 & G10 Digital Cameras
- ACK-DC60 AC Adapter Kit for Canon PowerShot A3000 IS and A3100IS Digital Cameras
