Abstract: In order to reduce the power consumption during the over-current of the DC/DC power supply chip, a high-precision oscillator with frequency shift is designed in this paper. When an overcurrent condition occurs in the chip, the oscillator frequency can be reduced to below 100 kHz. The circuit is simulated based on CSMC 0.25 μm 30 V-60 V BCD process. A sawtooth wave with a signal amplitude of 0.6 V~3.2 V and a frequency of 260 kHz can be obtained at normal temperature. Temperature deviation is within ±4.23%, power supply sensitivity deviation is within ±1.6%. When the process corner deviation occurs, the frequency of the oscillator is corrected by fuse trimming.