The output voltage can be greater or lower than the input voltage. One disadvantage of the buck and buck-boost topologies is that the switch is not referenced to ground, which makes the driver circuitry more complex. The buck-boost topology also inverts the sign of the output voltage, which brings another disadvantage when comes to a cost effective implementation of the sensing circuitry. The preferred method for implementing PFC and Interleaved PFC is the boost converter due to the reduced current ripple, simplicity of gate driver implementation, and also because it meets the requirements of output voltage. The discontinuous conduction mode of buck and buck-boost topologies would have a negative influence on the total harmonic distortion, or THD, and higher gate driver cost.