It's crucial that you are using 'active breathing' so that you can let go of 'holding' or tensions that are keeping you from releasing your voice with a relaxed, open sound.
Here’s a good exercise from my book From Shower To Stage…7 Easy Steps for Singing Like A Pro! I call the ‘Resting Pose Exercise’: lay on the floor, placing a book in the diaphragm area (in the center, just above and between the bottom of the ribcage). As you breathe in, 'fill up' with air so that the book rises. As you exhale, the book will lower as the diaphragm area flattens. Keep doing this exercise until this type of breathing becomes natural and habitual, and you can breathe this way standing up. As you sing or speak, 'fill up' with air and try to keep 'filled up' even as you're using your voice, although, naturally, with the exhalation of air, your diaphragm area will flatten somewhat.
Remember, your breath is your engine; never your throat. If you want power and volume, simply fill up with more air and use the 'cushion of air' as your vocal support mechanism.
And P.S. - breathe with a soft belly!