dbforge not working with sqlite

[eluser]Unknown[/eluser]
Hello guys

When I try to create a table in MySQL using dbforge, it works fine. But when I try to execute the same code to create a table in a sqlite database, it does not. The file "tb.db" is created, but no tables inside it.

Thanks a lot.

Here is the code

Code:

$fields = array(
      'id' => array(
                      'type'           => 'INT',
                      'constraint'     => 9,
                      'unsigned'       => TRUE,
                      'auto_increment' => TRUE
                     ),
      'nome' => array(
                      'type' => 'VARCHAR',
                      'constraint' => '100'
                     ),
      'usuario' => array(
                      'type' => 'VARCHAR',
                      'constraint' => '50'
                     ),
      'senha' => array(
                      'type' => 'VARCHAR',
                      'constraint' => '50',
                     ),
      'email' => array(
                      'type' => 'VARCHAR',
                      'constraint' => '200'
                     ),
      'sexo' => array(
                      'type' => 'CHAR',
                      'constraint' => '1'
                     ),
      'idade' => array(
                      'type' => 'INT',
                      'constraint' => '2',
                      'unsigned' => TRUE
                     ),
      'altura' => array(
                      'type' => 'VARCHAR',
                      'constraint' => '5'
                     ),
      'peso' => array(
                      'type' => 'INT',
                      'constraint' => '2',
                      'unsigned' => TRUE
                     ),
      'quadril' => array(
                      'type' => 'INT',
                      'constraint' => '2',
                      'unsigned' => TRUE
                     ),
      'busto' => array(
                      'type' => 'INT',
                      'constraint' => '2',
                      'unsigned' => TRUE
                     ),
      'telefone1' => array(
                      'type' => 'VARCHAR',
                      'constraint' => '20'
                     ),
      'telefone2' => array(
                      'type' => 'VARCHAR',
                      'constraint' => '20'
                     ),
      'cidade_id' => array(
                      'type' => 'INT',
                      'constraint' => '2',
                      'unsigned' => TRUE
                     ),
      'preco1' => array(
                      'type' => 'DECIMAL',
                      'constraint' => '10,2'
                     ),
      'preco2' => array(
                      'type' => 'DECIMAL',
                      'constraint' => '10,2'
                     ),
      'sn_viagem' => array(
                      'type' => 'CHAR',
                      'constraint' => '1'
                     ),
      'sn_cartao' => array(
                      'type' => 'CHAR',
                      'constraint' => '1'
                     ),
      'sn_ingles' => array(
                      'type' => 'CHAR',
                      'constraint' => '1'
                     ),
      'sn_frances' => array(
                      'type' => 'CHAR',
                      'constraint' => '1'
                     ),
      'sn_italiano' => array(
                      'type' => 'CHAR',
                      'constraint' => '1'
                     ),
      'sn_espanhol' => array(
                      'type' => 'CHAR',
                      'constraint' => '1'
                     ),
      'sn_completa' => array(
                      'type' => 'CHAR',
                      'constraint' => '1'
                     ),
      'sn_disponivel' => array(
                      'type' => 'CHAR',
                      'constraint' => '1'
                     ),
      'sn_ativo' => array(
                      'type' => 'CHAR',
                      'constraint' => '1'
                     ),
      'sn_homens' => array(
                      'type' => 'CHAR',
                      'constraint' => '1'
                     ),
      'sn_mulheres' => array(
                      'type' => 'CHAR',
                      'constraint' => '1'
                     ),
      'sn_casais' => array(
                      'type' => 'CHAR',
                      'constraint' => '1'
                     ),
      'sn_hoteis' => array(
                      'type' => 'CHAR',
                      'constraint' => '1'
                     ),
      'sn_moteis' => array(
                      'type' => 'CHAR',
                      'constraint' => '1'
                     ),
      'horario' => array(
                      'type' => 'VARCHAR',
                      'constraint' => '100'
                     ),
      'dia_vencto' => array(
                      'type' => 'INT',
                      'constraint' => '2',
                     ),
      'vl_mensal' => array(
                      'type' => 'DECIMAL',
                      'constraint' => '10,2'
                     ),
      'mensagem' => array(
                      'type' => 'text',
                     ),

    );
    $this->dbforge->add_field($fields);
    $this->dbforge->add_key('id',TRUE);
    $this->dbforge->add_key('nome',FALSE);
    $this->dbforge->add_key('usuario',TRUE);

    $this->dbforge->create_table('modelo');