Rapid control prototyping for server power supply with high-resolution PWM

Abstract

In this paper, we report the first rapid control prototyping (RCP) system with a sub-nanosecond (ns) high-resolution Pulse Width Modulation (PWM) for server power supply circuits. Conventional RCP systems are designed mainly for engine and motor control. Based on the relevant response time and control accuracy requirements, their PWM update periods and resolutions are over 100 microseconds (µs) and 100 ns, respectively. The shortest update time reported thus far is 12.5 µs. However, for server power supply, the required PWM update period and resolution are less than 10 µs and sub-ns, respectively. Therefore, we developed a new interface board with high-speed and high-resolution PWM output, which is connected between an under-development power supply board and a commercially available RCP machine to increase the RCP system's speed and resolution. Moreover, we have developed new software that improves data transfer latency and maintains a constant PWM update period. The combination of the new interface board, high-performance RCP machine, and new software realizes the required short PWM update period and high-resolution PWM of 6.5 µs and 0.15 ns, respectively. This is the shortest PWM update period reported yet, and it is adequate for operating server power supply. We applied the new RCP system to a 500 W full bridge converter with 100 kHz feedback control. Frequency response and soft start functions are easily confirmed by the new RCP system.