How to avoid refreshing the entire page by doing __doPostBack?

I have a call to an ASP button by means of __doPostBack, as you can see in the attached code, also try with trigger, but I still have the same result ... the entire page is refreshed.

How can I update only an update panel where the ASP button is contained?

  bootbox.dialog({
    title: "Validacion Paciente",
    message: "<input type='text' id='mensaje' class='border border-white' name='mensaje' style='display: none;'/><div id='content-capture' style='display: none;'> <div id='status'></div> <div id='imagediv' class='mb-2'></div> </div> <div id='Scores'>  <input type='hidden' id='qualityInputBox' size='10' style='background-color: #DCDCDC; text-align: center;'> </div>",        
    buttons: {
        main: {
            label: "Continuar",
            className: "btn-primary",
            callback: function () {

                __doPostBack('<%= btn_buscar.ClientID %>', 'OnClick');                    

                //$('btn_buscar').trigger('click');
            }
        }
    }
});