Automatically Open Popup Without Refreshing Parent?

I have the need to create a popup after a delay. The problem I'm getting is that the parent page is refreshing automatically from the action of creating the popup. I don't want the parent page to refresh!

This is what I currently have:

$popupScript = '
<script language="JavaScript">
setTimeout("window.open('index.php?do=renew','Popup1','toolbar=0, width=500, height=500')",' . $delay . ');
</script>';

The page is in php, so that's why I have it as a string, which I later pass to a template page.

This would simply be:

<script language="JavaScript">
setTimeout("window.open('index.php?do=renew','Popup1','toolbar=0, width=500, height=500')",6000);
</script>

... if it was placed straight into the HTML. Incidentally, it's included into the HTML HEAD area, not the body, as the original source of the script suggested: [URL]

$delay is the delay before the popup opens, in microseconds (so 6000 would be 6 seconds).

What can I do to have the same delayed auto-popup functionality, but without it automatically refreshing the parent page where the above code resides?

As some background to what I'm achieving: The issue with not wanting the parent page to refresh is that each time it does, the login session gets extended. The popup itself (which I already have working ok) provides a 'continue working' function, or close and refresh the parent is nothing has been done after a short period.