Abstract: DC-DC converters can simultaneously perform power conversion and data transmission. To address the challenge of lower communication rates limiting the application of power/data multiplexing transmission (PDMT), this paper proposes a novel scheme of joint power/carrier modulation (JPCM). Differing from traditional binary PDMT approaches, JPCM concurrently applies 2FSK modulation to both power and carrier, enabling parallel transmission of two data streams. This can be regarded as a quaternary FSK, effectively enhancing communication rates. In comparison to traditional quaternary PDMT schemes, the JPCM approach requires half the number of bandpass filters in the demodulation stage, resulting in reduced software overhead. First, the feasibility of PDMT is theoretically demonstrated. Subsequently, it configures different symbols by four distinct voltage ripple frequencies, and designs the schemes of JPCM encompassing high and low data bit modulation and data demodulation based on sliding discrete Fourier transform. Furthermore, the impact of output reference voltage transients on communication is critically analyzed, and dynamically adjusting the thresholds proves effective in suppressing symbol errors. Finally, an experimental setup consisting of two parallel Buck converters is established. Experimental results demonstrate that a communication rate of 20 kb/s can be achieved under steady-state, load transient, and output reference voltage transient conditions by PDMT, verifying the effectiveness of this scheme.