High Time-Resolution PWM Generator for GaN Converters

High time resolution is key to get the most out of Gallium Nitride (GaN) technology in designing fast and high efficiency power converters. High resolution digital pulse-width modulation (DPWM) can be used, but it needs to be designed with a reasonable operating frequency to avoid high dynamic power dissipation. In this paper, a DPWM based on a programmable delay unit implemented in a closed loop solution is presented. The loop ensures that the elements in the delay chain have the same delay enabling PVT variation rejection and result consistency without the need for a high operating frequency. This allows tuning signals with a resolution of 195 ps and a high linearity, making the unit compatible with the requirements for driving GaN power devices. The system has been implemented in a test chip using 100 V 0.13 μm BCD technology at 40 MHz operating frequency and validated with a custom debug board that confirms the expected resolution over a wide tuning range