STMicroelectronics Off-line LED Driver with Primary-Sensing STMicroelectronics Off-line LED Driver with Primary-Sensing is a high-voltage primary switcher intended for operating directly from the rectified mains with minimum external parts to provide an efficient, compact, and cost effective solution for LED driving. STMicroelectronics Off-line LED Driver with Primary-Sensing combines a high-performance low-voltage PWM controller chip and an 800V, avalanche-rugged power MOSFET in the same package. The PWM is a current-mode controller IC specifically designed for ZVS (zero voltage switching) fly-back LED drivers, with constant output current (CC) regulation using primary-sensing feedback. This eliminates the need for the opto-coupler, the secondary voltage reference, as well as the current sense on the secondary side, while still maintaining a good LED current accuracy. Moreover it guarantees a safe operation when a short circuit of one or more LEDs occurs. In addition, the device can also provide a constant output voltage regulation (CV), which makes the application able to work safely when the LED string opens due to a failure. Quasi-resonant operation is achieved by means of a transformer demagnetization sensing input that triggers the MOSFET's turn-on. This input also serves as both output voltage monitor to perform CV regulation, and input voltage monitor to achieve mains-independent CC regulation.