Research On Interleaved Boost Power Factor Correction Converter

Boost power factor corrector operated in Discontinuous-Inductor-Current Mode (DICM) is popular in low to moderate power level. The input current of this converter naturally follows the sinusoidal line voltage, therefore, the current control loop can be removed and the whole control loop is simplified. Moreover, Zero Current Switching (ZCS) is another advantage for DICM Boost PFC, it reduces power losses in the power switches and the snubber circuit which suppresses reverse recovery current of the output rectifier is not required. Although DICM boost PFC has many advantages, it is seldom adopted in high power application. The main reason is the pulsating input current which makes the design of input filter difficult. The problem can be solved by interleaving technique which effectively alleviates the ripple current, reduces switching stress and inductor area. So the power level of PFC stages can be greatly improved.This paper mainly studies interleaved boost PFC converters operating in DICM Mode and Critical Mode.Firstly, detailed analysis of the critical mode boost PFC circuit is performed. For this case, the power switch is always turned on immediately after the inductor current has reached zero and the on-time is fixed within a half line cycle. The interleaving technique is applied in the critical mode boost PFC converters, and its benefits are studied in the paper. Through the steady state analysis of the circuit, the equations of input ripple current are derived. These equations show how the input ripple current varies with changes in line voltage. Furthermore the output ripple voltage of the PFC converter is analyzed in detail by power matching theory.Secondly the small signal model of the interleaving boost PFC circuit in DICM is derived by State-Space Average Method. In this PFC converter, the performance of separated inductors and coupled inductors are analyzed respectively. Compared with separated inductors, the peak current in coupled inductors is large and the harmonic component of the input current is high. So novel integrated inductors are applied in this paper, and the PSpice model of integrated inductors is developed using the gyrator-capacitor approach. Through the simulation, we can see the drawbacks of coupled inductors can be overcome by the integrated inductors.Finally a simple interleaving control circuit is proposed for the variable frequency operation. This method can determines the activation point of the drive signal of the slave switch exactly, and its control logic is depicted in detail. This thesis also calculated the parameters of the main components in the Boost converter. In the end, simulations on the whole circuit are performed to validate the theory analysis, and the results show that high power factor and low noise can be achieved by the new interleaving technique without sacrificing efficiency.