| Abstract |
In the last few years, several low-cost Power Factor Correctors (PFC) control techniques operating in Continuous Conduction Mode (CCM) have been proposed in order to simplify the traditional control strategies based on an analog multiplier. This simplification makes sense in the case of relatively low-power and wide input voltage range applications. These techniques are focused in the Boost converter as a first stage of ac-dc power supplies. However, in some applications a PFC as a one-stage power supply can be used. This paper presents a new low cost control strategy suitable for Flyback family of converters (e.g., Buck-Boost, Flyback, SEPIC, Cuk and Zeta). The control is carried out by a low-cost standard IC controller for peak current-mode dc-dc converters. Neither analog multiplier nor input voltage sensor are needed to achieve quasi-sinusoidal line waveforms, which makes this method very attractive. In fact, this method is the application of the Linear Peak Current Mode Controller (LPCMC) to the Flyback family of converters. However, either it does not need the use of traditional two matched integrators or a current sensor with an integrator with reset for reducing the Total Harmonic Distortion (THD). In this case, the use of a simple exponential compensation ramp instead of linear one is the proposed solution for drawing a sinusoidal input current. Moreover, the line current is cycle-by-cycle controlled and, therefore, the input current feedback loop is extremely fast, which allows the use of this type of control with high frequency lines. An experimental prototype was developed as high Power Factor (PF) battery charger to verify the viability of the new control strategy. |
