RD-310 is a switch power supply reference design from Fairchild Semiconductor Corporation for mobile phone chargers. Its input voltage range is 90~265VAC, output voltage is 5V (0.7A), and rated output power is 3.5W. This design uses the main side regulation PWM control method and has the characteristics of low standby power (less than 30mW), high voltage startup, constant voltage (CV) and constant current (CC) control, frequency hopping to reduce EMI, cable voltage drop compensation, etc.