Form validation event trigger

Ionic Framework ionic-v3
1

Does anybody know whether there is a standard way in angular (2) of triggering form control validation onblur instead of onchange?
We use angular reactive forms. I can not find any configuration options for triggering validation onblur instead of onchange. Example:

this.loginForm = this.fb.group(
      {
        username: ['', [Validators.required]],
        password: ['', [Validators.required]],
      }
    );

Here the required-validators are triggered on any value change in the attached input elements. Is there a way to trigger the validators only onblur (i.e. when leaving the input element)?

Any ideas are appreciated!

Remarks: In angularjs we used ng-model-options:

ng-model-options="{ updateOn: 'blur' }"

2