A Switched Capacitor and Autotransformer Hybrid Converter with DC Current in the Windings
Cheng Li, Jose GE A. Cobos
Abstract
This article presents a hybrid converter combining soft-charged switched capacitors and an autotransformer with dc current in the windings, optimized for 4:1 fixed voltage gain conversion (DCX) for high output current. By adding an additional output inductor, it can also regulate the output voltage to lower than ¼ of the input voltage by changing the duty cycle. The switched capacitors voltage and the two winding currents in the transformer are auto-balanced. Nonresonant operation of the circuit enables dc current in the windings and simplifies both transformer and circuit design. Experimental results for 48 V–12 V DCX operation achieve 98% peak efficiency and 97.7% full load (250W) efficiency. Regulation by using the output inductor is verified experimentally up to 48–6V (8:1) voltage step down.