Implementação de um PWM digital de alta resolução e frequência utilizando circuito de atraso

Abstract

This paper presents the design of a high resolution and high frequency digital PWM based on a delay circuit, which will be part of a digital control system that could replace in future the analog control system presently used in the power supplies of the National Labora-tory of Synchrotron Light. These power supplies are responsible for driving many equipment of the electron storage ring, such as bending magnets, quadrupoles, sextupoles and steering magnets. Analog control systems are susceptible to noise and xposed to ambient temperature variations. Both are responsible for the change of electrical parameters that cause loss of accu-racy. Digital control systems have some advantages over analog systems, such as versatility, ease of adjusting parameters, among others. In this project we used a microcontroller that has an internal PWM module with 10-bit resolution and switching frequency in the tens of kHz. After passing through a delay circuit, it can achieve 18-bits of resolution and the frequency remains constant. In order to test the control system, we developed a computer interface in Matlab to fa-cilitate communication between the user and the hardware. We used standard RS232 as serial communications. The software sends information to the microcontroller, receives data, pro-cess it, and then acts on a witch by PWM. The design was prototyped and implemented on an IGBT in order to drive an RL load. With a DCCT we measured the variation of current as a function of the variation in the time that the switch remained on, in order to prove the system resolution. The results are presented and analyzed, validating the proposed design.