I set up a windows scheduled task to auto-update the working directory from SVN repository but it kept failing. Finally got it working and here is the svn update command I used:
svn update –non-interactive –trust-server-cert –no-auth-cache –username [username] –password [pswd] “[Path]”

If you choose to let it run without asking user to logon, you have to pass in trust-server-cert parameter. Otherwise it will fail.