In this paper, an improved KY converter with pulse width modulation (PWM) is proposed. The reverse current paths under discontinuous-conduction mode (DCM) are analyzed. To eliminate the reverse current exactly, a noval zero current detection (ZCD) method is proposed and demonstrated. The KY converter is fabricated by using 0.18 $\mu$ m BCD process with active area of 3.4 mm 2 . The off-chip components of an inductor of 4.7 $\mu$ H, a load capacitor of 4.7 $\mu$ F and two flying capacitors of 100 $\mu$ F are employed. Simulated results show that the designed ZCD can work well in DCM of the proposed converter. The power conversion efficiency (PCE) can be maintained above 90% over wide load range from 100 mA to 2 A, and the PCE is enhanced by 16.3% compared with w/o ZCD at 25 mA load current.