J'ai effectivement suivi cet exemple et cela a fonctionné pour moi :)
NameVirtualHost *:80
<VirtualHost *:80>
   ServerName mysite.example.com
   Redirect permanent / https://mysite.example.com/
</VirtualHost>
<VirtualHost _default_:443>
   ServerName mysite.example.com
  DocumentRoot /usr/local/apache2/htdocs
  SSLEngine On
 # etc...
</VirtualHost>
Faites ensuite :
 /etc/init.d/httpd restart 
RewriteEngine On
RewriteCond %{HTTPS} off
RewriteRule ^ https://%{HTTP_HOST}%{REQUEST_URI}
http://www.sslshopper.com/apache-redirect-http-to-https.html
ou
http://www.cyberciti.biz/tips/howto-apache-force-https-secure-connections.html