The field-weakening control technology is of great significance for expanding the speed control range of permanent magnet synchronous motors. In deep field-weakening operation, if the current regulator saturates, it can cause the motor to lose control or even be damaged. This article studies the causes of current loss of control in field-weakening control and points out that accurate limiting of d-axis current and MTPV control is of great significance in preventing system loss of control. Based on the above analysis, this article proposes a control strategy to achieve the MTPV trajectory without extra regulators. The proposed control strategy has been experimentally verified to significantly improve the field-weakening speed range of permanent magnet synchronous motors.