__doPostBack() is causing post pack but not calling button click event in aspx page

__doPostBack() is causing post pack but not calling button click event in
aspx page

I am using a aspx page which is having a button.
<asp:Button ID="savebtn" runat="server" OnClick="savebtn_Click"
Style="display: none" />
There are two ways to cause post pack as shown in the below code.
$(document).ready(function () {
var id = document.getElementById('<%= savebtn.ClientID %>');
//Cause post back & calls page load but not savebtn_Click event
__doPostBack('<%= savebtn.ClientID %>', 'OnClick');
});
$(document).ready(function () {
var id = document.getElementById('<%=
savebtn.ClientID %>');
//Cuase postback & calls both PageLoad and savebtn_Click events.
//If I use method, There is no way to know which control caused
postback
id.click();
});
When I use __doPostBack, It calls page load event but not btn click event.
Is there any way using __doPostBack to trigger Page Load as well as
savebtn_Click event.
If I use id.click(); as shown above, I am able to call savebtn_Click but
it does not tells me which control caused the post back.
Please help.