Existing studies of current limiting control for grid-forming inverters mostly focus on grid-forming inverters that use the multi-loop control structure. This paper describes a current limiting control for grid-forming inverters that use the single-loop control structure. The proposed current limiting control is implemented at the PWM control layer to guarantee the fast response. Once detecting the overcurrent caused by severe faults, the proposed control strategy immediately blocks relevant IGBTs using a hysteresis loop, ensuring the overcurrent can be limited within a few PWM cycles. After the fault is cleared, the inverter seamlessly transfers back to the droop control mode to maintain the stability. The current limiting control has been tested in a microgrid environment in the OPAL-RT platform. Study results show that the control strategy can effectively limit the overcurrent under both balanced and unbalanced faults, and the system transient stability can be maintained after the fault is cleared.