Loading a Database in CodeIgniter - postgresql

Question

I want to connect to a postgresql database in CodeIgniter via the pdo-driver.
Doing it manually works without any Problems:
$gp = new PDO("pgsql:host=pdca.example.de;port=5432;sslmode=require;dbname=dssprod;",$techUser,$techPW);
$query = $gp->query('select * from table limit 10');
$result = $query->fetchAll( PDO::FETCH_ASSOC );
var_dump($result);
doing the same within CodeIgniter in config\database.php :
$active_group = 'default';
$db['default'] = array(
'dsn' => "pgsql:host=pdca.example.de;port=5432;sslmode=require;dbname=dssprod;",
'username' => $techUser,
'password' => $techPW,
'dbdriver' => 'pdo'
);
and then in a view:
$connect = $this -> load -> database();
var_dump($connect);
--> results in a bool(false)
I can't get a Connection to the db with CodeIgniter, any idea why?
--- edit ---
I tried a config without pdo, same result (false).
$active_group = 'default';
$db['default'] = array(
'hostname' => 'pdca.example.de',
'port' => 5432,
'sslmode' => 'require',
'username' => $techUser,
'password' => $techPW,
'database' => 'dssprod',
'dbdriver' => 'postgre',
'dbprefix' => '',
'pconnect' => FALSE,
'cache_on' => FALSE,
'cachedir' => '',
'char_set' => 'utf8',
'dbcollat' => 'utf8_general_ci',
'swap_pre' => '',
'encrypt' => FALSE,
'compress' => FALSE,
'stricton' => FALSE,
'save_queries' => FALSE
);