Switching the TV on using an APP

I am looking to develop an application to work with smart and android TV. The app would initially reside on a USB device. I have Tizen but I am not restricted to using Tizen.

Please tell me what API can be called to start the TV from a standby mode at a preset time and play a video.

I know that switching the TV on functionality exist using smarththings app (device) but what API is used to switch on the TV.
Thanks for your help.