SDH8634 is a current mode PWM+PFM controller with built-in high voltage MOSFET and high voltage startup current source, external sampling resistor. SDH8634 has built-in high voltage startup current source, low standby power <30mW. There are many control modes: in heavy load, working in PWM mode; in light load, working in PFM mode to improve conversion efficiency; in idle, enter hiccup mode to reduce standby power. SDH8634 has jitter function to reduce EMI. The built-in peak current compensation circuit can make the limit output power consistent when different AC input voltages. The built-in soft start function can reduce the stress of the transformer during power-on and prevent the transformer from saturation. SDH8634 integrates a comprehensive abnormal state protection function, including leading edge blanking (LEB), pulse-by-pulse peak limiting, VCC overvoltage protection (OVP), output overcurrent protection (OLP) and overtemperature protection (OTP).