A novel type of high efficiency, high power density and high reliability switching power supply system based on LD7532A PWM control chip is designed and realized by using single end flyback converter structure and current continuous working mode. The input voltage of the power supply is AC 90V~264V, the working frequency is 65kHz, the output power is 40W, and the output voltage is 19V. The test results show that the efficiency of the switch power system is above 85.7%, the no-load loss is less than 0.3W, the output ripple of full load is less than 60mV, and the output voltage is fairly stable.