The project described here outputs 12V DC voltage from the input of 230V AC. The output current is up to 100mA. The project is based on BM2P129TF chip which is PWM method DC/DC converter with a built-in 650V MOSFET. BM2P129TF contributes to low power consumption by built-in a 650V starting circuit. Built-in current detection resistor realizes compact power supply design. Current mode control imposes current limitation on every cycle, providing superior performance in bandwidth and transient response. The switching frequency is 100Khz in fixed mode. At light load, frequency is reduced and high efficiency is realized. Built-in frequency hopping function contributes to low EMI. Low on-resistance 9.5 Ohms 650V MOSFET built-in contributes to low power consumption. The default over current limit of the chip is 450mA.