Replacing my WNAP320 with a WAC540 POE Issues with FS728TP Switch

I'm looking to replace my ageing WNAP320 access point with a WAC540 connected to my current FS728TP switch, but when I check the POE requirements it says that for optimum performance I need a switch meeting the 802.3at standard. However my current switch is only a 802.3af switch so do I need to replace the switch or is there an injector I can use with my current POE switch to meet the higher specification or any other options.

Any advice would be greatly appreciated....