The AP1684 is a high performance AC-DC power factor corrected LED driver controller which is driving high voltage bipolar transistor. The device uses Pulse Frequency Modulation (PFM) technology to regulate output current while achieving high power factor and low THD. It operates as a boundary condition mode (BCM) buck controller which is good for EMI. The AP1684 provides accurate constant current (CC) regulation while removing the opto-coupler and secondary control circuitry. It also eliminates the need of loop compensation circuitry while maintaining stability. It can meet the requirement of IEC6100-3-2 harmonic standard. The AP1684 features low start-up current, low operation current and high voltage driving bipolar transistor. It adopts dynamic base driver control technology and valley on switching mode to achieve high efficiency. It also has rich protection features including over voltage, short circuit, over temperature protection.