The current portable ECG acquisition system needs analog to digital conversion module, which has low power consumption and high resolution. Although the analog to information converter (AIC) based on pulse width modulation can effectively reduce the sampling rate of the system, the quantization part of the conversion clock is proportional to the quantization accuracy. Therefore, there is a problem of high power consumption. In this study, a precision adjustable time to digital conversion (TDC) module based on the power entropy is proposed, which is based on the energy imbalance of ECG signal. The energy maximization is taken as the basic principle of design. The minimum quantization accuracy of system observation vector is determined by analyzing the power spectrum entropy of ECG signal. In this way, the optimal design of AIC time coding system is achieved. Experimental results show that this method can reduce 80% TDC clock dynamic reversal while sampling ECG signals under the conditions of compression ratio of 4, SNR of 38. 91 dB and reconstruction accuracy of 0. 36% . Therefore, the power consumption can be reduced effectively.