Current-detecting method for overcoming the limitations of lower-arm current detection

A current detection method adapted to an inverter, comprising:

• executing a compensation method, wherein the compensation method comprises:
• determining whether the conduction periods of any one of the lower arms is less than a lower limit value when the lower arms are turned on simultaneously;
• calculating a first difference when it is determined that a first conduction period of a first lower arm of the inverter is less than the lower limit value, wherein the first difference is equal to a difference between a lower limit set value and the first conduction period;
• and
• adding the first difference to all the conduction periods of other lower arms of the inverter;
• determining that a plurality of lower arms have a minimum conduction period when the lower arms of the inverter are turned on simultaneously;
• determining a sampling time point according to the minimum conduction period, wherein a sampling period is defined as a period from a starting point of the minimum conduction period to the sampling time point, wherein the sampling period is close to the minimum conduction period;
• simultaneously detecting currents flowing through the lower arms by a plurality of detection resistors to generate a plurality of measurement voltages;
• sampling the measurement voltages at the sampling time point;
• and
• determining currents of the inverter according to the sampled measurement voltages.