High precision control technique for constant current regulation in primary-side regulation systems

A constant current control technique for a primary-side control system is proposed to realise high precision output current regulation. With the novel ring detect and demagnetisation portion control technique, the ending time of demagnetisation can be accurately determined and the portion of demagnetisation in a switching period remains precisely the same. The simulation results show that with this control technique, the variation of output current is less than ±1.5% of the target value.