$pdf = new  TCPDF(PDF_PAGE_ORIENTATION, PDF_UNIT, PDF_PAGE_FORMAT, true, 'UTF-8', false);
$pdf->SetCreator(PDF_CREATOR);
$pdf->setPrintHeader(false);
$pdf->setFooterFont([PDF_FONT_NAME_DATA, "", PDF_FONT_SIZE_DATA]);
$pdf->SetDefaultMonospacedFont(PDF_FONT_MONOSPACED);
$pdf->SetFooterMargin(PDF_MARGIN_FOOTER);
$pdf->SetAutoPageBreak(true, PDF_MARGIN_BOTTOM);
$pdf->setImageScale(PDF_IMAGE_SCALE_RATIO);
$pdf->AddPage();
$html = '<h1>Türkçe Karakter</h1>';
$pdf->writeHTML($html, true, false, true, false, '');