In today’s modern era low power factor (PF) is major issue in the field of power electronics which has made our life, simpler, easier and comfortable. However, with this comfort and easiness this technology brings power quality issues because it is centered on solid-state devices. These issues introduce harmonic contained current or distorted current which has several drawbacks like high power loss, voltage distortion and EMI compatibility issues etc. The conventional boundary conduction mode (BCM) integrated buck-boost converter (BBC) operating with constant on-time control (COT) control scheme have low PF with high total harmonic distortion (THD) because of harmonic contained input current waveform. So, in order to make the input current waveform as a sinusoidal by changing the on-time of only buck switch, a modified variable-on-time (VOT) control scheme for Integrated BBC is proposed in this paper. The VOT control scheme can achieve high PF with low THD by utilizing the input and output voltage to modulate the on-time of only buck switch. The theoretical analysis is given, and the simulation results confirm the advantages of the proposed control scheme. The object of the research paper is to propose the control scheme to realize unity PF for CRM buck converter by only modulating the on-time of buck switch. The research methodology is based on: Input PF analysis of buck converter with traditional control scheme; Introduction of proposed control scheme; comparative analysis and simulation results to show the effectiveness of proposed control scheme.