DCM Operating Characteristics and Harmonic Suppression Study of AC-DC Converter

The input current of AC-DC converter is spike under the light load, and its harmonic components are massive, which are harmful to power quality. Based on the request of low cost and high performance HID lamp electronic ballast and miniwatt switching supply, the mathematical model of AC-DC power conversion circuit working in discontinuous conduction mode (DCM) is established, the equations between input voltage, reference voltage and duty cycle are derived, the operating conditions in different states are analyzed, the changing rules between inductor current and duty cycle are studied. A type of active power factor correction (APFC) circuit based on the addition principle is designed by using peak current mode PWM controller, the operating characteristics in DCM, critical conduction mode (CRM) and continuous conduction mode (CCM) are simulated and analyzed, and the correctness of conclusion is verified. The result of spectral analysis for input current waveform shows that power factor of AC-DC converter is improved and the harmonic suppression effect of APFC circuit is obvious.