Hi.
If the TV stays in stand-by, with the LED light on, but does not respond to remote, or to the buttons on the chassis, then the TV has gone in protect (safe) mode because an internal fault had been detected.
In that case the TV is faulty.
In your case 3 blinks on Bravia KDL models mean that an abnormal voltage from power board to the digital board had been detected.
This may be a temporary problem, caused for example by a power surge, but may also mean that either power board, or digital controller board may be defective.
Follow the troubleshooting on this article:
Why my TV does not start up and remains in... If that does not work, contact Sony, ringing the support number listed on the owners manual to get the TV repaired by a licensed technician.
Regards.
G