Journal article: The literature on ascending combinatorial auctions yields conflicting insights regarding the possibility to implement the Vickrey payoffs for general valuations. We introduce the class of minimal ascending auctions, a class which allows one to disconnect the final payments from the final bids but which prohibits the raising of the price vector of a provisionally winning bidder. We first establish the impossibility of implementing the Vickrey payoffs for general valuations. Second, we propose a minimal ascending auction that yields a bidder-optimal competitive equilibrium thanks to payment discounts.