codeigniter mysql不时更新惩罚

I have this at my model, I want to update the price everynow and then, I want that everytime I open the controller it will add up 100 to the Penalty, how do I do that? what is wrong with my query? Probably because of the update right? I dont know plz help! If I put 200 at 'Penalty' + 200 it will go for 200 and then if I put 100 it puts 100 again

public function addPenalty(){
    $data = array(
        'Penalty' => 'Penalty' + 100
        );
    $this->db->where('Active',1);
    $query = $this->db->update('tbl_client_penalties',$data);
    return $query;
}

Try this code

$this->db->set('Penalty', 'Penalty + '.100, FALSE);
$this->db->where('Active',1);
$this->db->update('tbl_client_penalties');

for more information check the document.

Try this code

$dbdata["Penalty"] = "Penalty + 100";
$this->db->update("tbl_client_penalties", $dbdata, array('Active' => 1));