In order to support a higher peak data rate, carrier aggregation (CA) is implemented into Long Term Evolution Advanced (LTE-A) systems to provide sufficient bandwidth for data transmission. In Time Division Duplexing (TDD) CA systems, aggregation of Component Carriers (CCs) with different TDD configurations is necessary due to the coexistence with legacy TDD systems. To achieve the peak data rate of Secondary Cell (SCell) in case of cross-carrier scheduling, the Physical Downlink Shared CHannel (PDSCH) hybrid automatic repeat request (HARQ) timing of SCell should follow its own PDSCH HARQ timing. Meanwhile, Primary Cell (PCell) still uses its own PDSCH HARQ timing. However, using different PDSCH HARQ timing between PCell and SCell may lead to Physical Uplink Control CHannel (PUCCH) resource mapping collision, which sacrifices downlink (DL) peak data rate and increases transmission latency for the reason of PDSCH HARQ feedback failure. In this paper, a new implicit PUCCH resource mapping method is proposed to avoid PUCCH collision in inter-band TDD CA systems. ENB and user equipment (UE) re-allocate PUCCH resources for each DL subframe on SCell. By using this proposal, PUCCH collision for cross-carrier scheduling in TDD CA systems can be completely eliminated without introducing significant PUCCH overhead increase.