The changes in electronic structures generating large dipole derivatives for the CC stretches in charged conjugated (pi-electron) hydrocarbon species are analyzed theoretically by deriving a relation between dipole derivatives and electric-field-induced changes in bond orders and by constructing a simple model Hamiltonian; The model Hamiltonian consists of the diagonal term representing the electric-field dependence of the energy on each site (carbon atom) and the off-diagonal term taken from the Su-Schrieffer-Heeger model. It is shown that the dipole derivatives calculated with the model Hamiltonian are in reasonable agreement with those obtained at the B3LYP/6-311G* level of density functional theory. It is concluded that the model Hamiltonian adequately describes the mechanisms that determine the signs and magnitudes of the dipole derivatives of the CC stretches in charged conjugated hydrocarbon species. For neutral species, the dipole derivatives of all the CC stretches are calculated to be zero by the model Hamiltonian. This is a consequence of the pairing theorem that holds for the molecular orbitals of the model Hamiltonian for alternant hydrocarbons and is consistent with the experimental results that the IR intensities are weak in the fingerprint region for neutral species. As examples of the application of the present approach, detailed analyses of the changes in the electronic structures generating dipole derivatives of the CC stretches are carried out for the radical cations of naphthalene, pentacene, biphenyl, perylene, and biphenylene, as well as for some related species.