| Power factor correction (PFC) techniques have received considerable attention in ac-dc converter, due to its ability to reduce input current distortion, which helps electrical equipments decrease the noise and heat during operation. Recently, besides high input PF required, there is increasing demand of low output ripple in PFC converters applications, such as in programmable output adapters, and LED lighting drivers. Thus, it is important to develop high input power factor (PF) and low output ripple PFC converters.In this paper, quadratic Boost topology is utilized to realize PFC and the converter performance is investigated. Compared to discontinuous conduction mode (DCM) Boost PFC converter, when input inductor and storage inductor both operate in DCM, quadratic DCM-DCM Boost PFC converter has much lower output voltage ripple. This paper analyzes the operation principle of quadratic DCM-DCM Boost PFC converter in detail, and derives the expression of output voltage ripple and PF. It is theoretically verified that compared to traditional DCM Boost PFC converter, quadratic DCM-DCM Boost PFC converter has much lower output voltage ripple.However, quadratic DCM-DCM Boost PFC has worse PF than that of traditional DCM Boost PFC converter. When input inductor L1 operates in DCM, by analyzing PF expression of quadratic Boost PFC converter, this paper points out that PF can be improved by increasing middle capacitor voltage. Further, the influence of storage inductor on middle capacitor voltage and its voltage ripple are studied, which indicate that when storage inductor L2 operates in DCM, quadratic DCM-DCM Boost converter can achieve higher PF and lower output voltage ripple by setting appropriate inductor ratio of L2/L1.In order to obtain higher PF, this paper analyzes expressions of PF and input inductor current more specifically, and proposes variable duty cycle control for quadratic DCM-DCM Boost PFC converter. An approximation equivalent for the variable duty cycle is employed to simplify the implementation circuit. Besides, expressions of PF and the output voltage ripple are derived. In 100-240V input voltage range, the PF of quadratic DCM-DCM Boost PFC converter with variable duty cycle control is very high, meanwhile the converter demonstrates small input inductor current ripple and low output voltage ripple, which illustrates that the converter achieves high power factor and low output voltage ripple. |
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