The NCL30002 is a switch mode power supply controller intended for low to medium power single stage power factor (PF) corrected LED Drivers. The device operates as a critical conduction mode(CrM) buck controller to regulate LED current at a high power factor for a specific line voltage range. The current limit threshold is tightly trimmed allowing open loop control techniques to reduce parts count while maintaining accurate current regulation and high power factor. CrM operation is particularly suited for LED applications as very high efficiency can be achieved even at low power levels. These are important in LED lighting to comply with regulatory requirements and meet overall system luminous efficacy requirements. In CrM, the switching frequency will vary with line and load. Switching losses are low as recovery losses in the output rectifier are negligible since the current goes to zero prior to reactivating the main MOSFET switch.