Acidic nature order among H3PO2, H3PO3, H3PO4and the reason?

Acidic strength : H3PO2> H3PO3 >H3PO4

H3PO2 is more acidic than H3PO3 and H3PO4The acid strength of an acid depends on the number of replacable hydrogens it gives per mole of the acid .We can say that H3PO2 gives only one replacable hydrogen while the other two dont give replacable hydrogens(as they are enclosed in a strong Hydrogen bond),Also O-H bond is stronger thanP-H bond due to the electronegative difference between hydrogen and oxygen (greater than the electronegative difference between hydrogen and phosphorus)hence O-H bond is stronger.