Pulsed phase cannons were an improvement of the previous phase cannon technology which Starfleet had developed by 2154.
Among the first starships to be equipped with this improved cannon was the Columbia. Along with ventral and dorsal torpedo launchers, pulsed phase cannons were one of the weapon upgrades recommended by Enterprise Captain Jonathan Archer. (ENT: "Home")
The specifications of the pulsed phase cannons were never made clear, nor was it revealed whether or not Enterprise was equipped with the weapons. When Columbia was seen firing its cannons in ENT: "Divergence", the energy beam was streamed like that of the previous cannon, suggesting that pulsed phase cannons simply fired a more powerful beam of energy than its predecessors.