A Shoot-Through-Free 180-MHz Isolated Converter With PG-Downsized PA for Low EMI

This article presents a 180-MHz low electromagnetic interference (EMI) isolated dc-dc converter using a $P_{\mathrm { G}}$ -downsized Class-D power amplifier (PA). This PA features a symmetrical topology that effectively cancels dipole emissions, while its series inductors placed between the cross-connected high-side and low-side transistors that inherently block shoot-through currents. To address the resulting degeneration states of oscillation, we introduce small, actively driven transistors, whereas the original power transistors operate in a passively driven manner, with their gate charge recycled like in a Class-D oscillator. This preserves the advantage of low gate drive loss ( $P_{\mathrm { G}}$ ) in high-frequency oscillators. The frequency misalignment between the switching and oscillation frequencies leads to only minor efficiency degradation. This eliminates the requirement for switching frequency calibration, while enables the low-complexity frequency hopping to further reduce EMI. We fabricated the PA and the receiver (RX) chips using 0.18- $\boldsymbol {\mu }$ m bipolar–CMOS–DMOS (BCD) process and attached them with a 14.4-mm $\boldsymbol {^{2}}$ PCB transformer. The converter achieves a 45.3% peak efficiency and a maximum output power of 1 W. It complies with the CISPR-32 Class-B standard.