# Current-Sensing Topology with Multi Resistors in Parallel and Its Protection Circuit
###### Abstract  
Current-sensing topology with multi resistors in series has limitations in improving the dynamic range of current acquisition, so a sensing topology with multi resistors in parallel is proposed. The overcurrent state of a parallel shunt circuit cannot be latched, resulting in protection hiccups. A dual threshold-detection circuit is designed to achieve protection state labeling and self-recovery. The rectified mean circuit is applied for overcurrent magnitude detection and its validity is proved. But the delay and ripple of the output waveform of the rectified mean circuit may also cause protection hiccups. Combining Fourier series representation, Fourier transform and inverse transform, the time domain expressions of the output of the rectified mean circuit for three common waveforms are obtained. Furthermore, the estimation formulas for the residual ripple amplitude of the three waveforms are derived. In an experiment, the protection hiccup issue in parallel sensing topology was eliminated, while the time constants and hysteresis ratios of the protection circuits were properly set according to theoretical calculation results. With five parallel sensing resistors, the ratio of the maximum to minimum range of the single current channel reaches \(1.28\times 10^{4}\), which is higher than counterparts with multiple series sensing resistors. The advantages of parallel sensing topology in improving dynamic range are confirmed. parallel resistors; current sensing; dynamic range; protection hiccup; rectified mean value +
Footnote †: journal: Applied  
**Citation:** [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON] Current-Sensing Topology with Multi Resistors in Parallel and Its Protection Circuit. **Appl. Sci. 2023, 13, 8382. [[https://doi.org/10.3390/app13148382](https://doi.org/10.3390/app13148382)]([https://doi.org/10.3390/app13148382](https://doi.org/10.3390/app13148382))**  
**Citation:** [PERSON]; [PERSON]; [PERSON], [PERSON]; [PERSON]; [PERSON], [PERSON] Current-Sensing Topology with Multi Resistors in Parallel and Its Protection Circuit. **Appl. Sci. 2023, 13, 8382. [[https://doi.org/10.3390/app13148382](https://doi.org/10.3390/app13148382)]([https://doi.org/10.3390/app13148382](https://doi.org/10.3390/app13148382))**  
**Citation:** [PERSON]; [PERSON]; [PERSON], [PERSON]; [PERSON]; [PERSON] Current-Sensing Topology with Multi Resistors in Parallel and Its Protection Circuit. **Appl. Sci. 2023, 13, 8382. [[https://doi.org/10.3390/app13148382](https://doi.org/10.3390/app13148382)]([https://doi.org/10.3390/app13148382](https://doi.org/10.3390/app13148382))**  
In order to meet the large dynamic range requirement in current measurement, multiple sensing resistors were used in current channel design [15; 16] or multiple current modules were designed [17; 18] to achieve multiple ranges. As far as we know, the multiple sensing resistors in existing studies in the literature were connected in series [15; 16; 19; 20]. The current flows through each resistor or its bypass circuit, so one of them must be capable of conducting the maximum allowed current in the maximum range. The increase in number of current sense resistors will lead to a tremendous increase in layout space and heat consumption. When the number of current sense resistors exceeds two, parallel connection would be a better choice. But the design of an overcurrent protection circuit is far more complicated than that of a series circuit. The input stage of most electrical equipment items is an AC-DC rectifier [21]. If a power factor correction (PFC) circuit is not applied in the rectifier, the current shape will be significantly different from a sine wave, but with narrow pulses [22]. In cases of power supply testing, there are also various non-sinusoidal current waveforms existing, such as triangular, pulse and rectangular waves [23]. These waveforms have various crest factors. In order to meet the requirement of common waveform measurement, a high peak factor, such as 3, was selected for channel circuit design [16; 17; 18].