Design Of High Accuracy Current Sensing Circuit For DC-DC Converter

With the progress of design and manufacture in integrated circuits,more and more electronic devices, such as smart phones, wearable devices and tablet PC are becoming smaller, lighter and smarter. These electronic devices fail to work without the power chip. As the function of electronic devices becomes continuously multiplied, the demand of power chip is increased constantly. Therefore, how to manufacture efficient and low-power power chip turns one of the significant projects in the research.Due to its efficiency and low power consumption, DC-DC converter, which is one kind of power management chip, obtains a broader use in electronic fields.Hence, current sensing circuits, as an important part of DC-DC converter, play a vital role in converter’s over-current protection and feedback loop in current controlled mode.At the bases of concluding domestic and overseas reality of development in current sensing technology and analyzing advantages as well as disadvantages of traditional current sensing technology, an improved high accuracy on-chip current sensor is proposed. It perfects the current sharing and loop gain in traditional current sensor, thus improves the accuracy of current sensor. The process characteristics, input voltage characteristics and loop gain characteristic for the improved current sensing circuit is simulated by simulation tools in Cadence. Results show that the accuracy of improved current sensor is over 95% and the highest of which reaches up to 99% in different temperature and process corner. When the range of input voltage is from 1.62V to 2.0V, the change for sensing accuracy of current is very small, which is basically at around 98% and indicates that sensing accuracy of current is still high when input voltage changes. Through simulation, we can see that the loop gain is 42dB, the phase margin is 45 degrees and the bandwidth is 80MHz, which shows that the circuit has good response speed and loop gain. Finally, compared with conventional current sensing circuit and the typical circuit in the reference in recent years, the simulation results show that the sensing accuracy of the improved current sensing circuit is improved.