Coded PWM Based Switching Ripple Communication Applied in Visible Light Communication

Visible light communication (VLC) system integrates LED lighting with wireless communication. Conventionally, power conversion and communication are designed separately. The circuitry added for communication helps to achieve a high bit rate, but increases costs and impacts the efficiency. On the other hand, power conversion and communication can also be designed together by applying switching ripple communication (SRC), where no additional devices are needed. However, SRC is usually achieved by broadband modulation methods, which means that the bandwidth is much lower than the switching frequency. By applying information theory to pulse width modulation (PWM), this paper proposes a novel VLC scheme that applies baseband modulation to SRC in order to achieve a high bit rate with a relatively low switching frequency. In addition, power control and communication are decoupled, so that they do not influence each other. In the experiments, GaN MOSFETs are used to achieve a 1.25Mbps VLC system with a code error ratio of less than 10-6. Moreover, the scheme shows good performance under the duty cycle from 70% to 30%, and under the output power from 100% to 7.5% of the rated value.