Hefei synchrotron radiation Light Source (HLS) presently has three kickers for electron injection. It is a lattice-dependent system, and different lattices will form different shapes of bump orbits. In the upgrading of HLS, a compact, lattice-independent injection system will be adopted. This paper looks into the possibilities of using quadrupole-magnet trim coils to produce assistant DC injection bumps and then to decrease the required amplitude of kicker bump. Some calculation results of injection schemes are discussed.