Yes, most AC powered flash units use voltage doubler or trippler circuits to charge the capacitor bank to a higher than'normal' voltage than what one gets when you 'just' rectify standard AC to DC. So in a nut shell they are designed for the voltage they are sold to be used at.

Mr. Rusty's words are true, but I have some concerns that consumer grade portable voltage convertors may be stressed by the high inrush currents that the flash electronics suck in right after the flash has be triggered.