Novel single-switch Isolated 42V/1kW Battery Charger Module uses Converter operating at near-unity Power Factor

摘要

The paper describes an integrated "smart" 42V battery charger module that can deliver up to 1kW at near-unity power factor. Power factor correction, step-down conversion, output voltage regulation, current limiting and galvanic isolation are all achieved from a single-switch transformer-coupled buck converter. This configuration makes use of a novel control algorithm employing both duty-cycle modulation and fixed duty-cycle switching at two distinct frequencies. In operation, the converter multiplexes between pure flyback and a composite flyback/forward mode, as the rectified sinewave input voltage drops below or rises above the reflected output voltage. Harmonics injected into the mains and peak currents carried by the semiconductors are both much lower than in previous versions of the topology. This innovative control strategy is highly suitable for AC-mains driven buck applications like battery chargers and UPS, both characterized by high-current outputs at low (12-48VDC) outputs. Full theory of operation is presented in the paper, supplemented by PSPICE simulation of a 1kW 48Vdc prototype. Given its small number of low-loss active devices -one APT Generation 7 PowerMOSFET, an APT Schottky-diode equipped secondary rectifier and a mains bridge, this configuration lends itself to integration as a compact and inexpensive power module with modest thermal management needs. The state-of-the-art fabrication techniques adopted by APTE to produce this Application Specific Power Module (ASPM) are described fully, along with experimental results from a prototype 500W/42V battery charger.