DER-405 - 25 W high efficiency (>90%), high power factor (>0.97) non-isolated LED driver for T10 tubes

This document describes a non-isolated, power factor corrected, low THD, high-efficiency LED driver that can provide 144 V, 180 mA drive for LED light strings within an input voltage range of 90 VAC to 265 VAC. LYTSwitch-4 uses advanced technology to enable single-stage power factor corrected LED driver design and primary-side constant current control in a cost-effective manner. The LYTSwitch-4 controller is ideal for LED driver applications and requires minimal external components. It provides output current control without the use of an optocoupler. LYTSwitch-4 integrates a 725 V power MOSFET and controller in a single chip. The controller includes an oscillator, PWM (Pulse Width Modulation), 6 V regulator, over-temperature protection, frequency dithering, cycle-by-cycle current limit, other protection features, and a charge controller for output CC (Constant Current) control . LYTSwitch-4 provides a range of sophisticated protection features, including control loop open/short circuit and automatic restart under output short circuit conditions. Precise hysteretic thermal shutdown ensures PCB board temperatures remain within safe limits under all conditions. The non-isolated, power factor corrected, buck-boost design presented in this report shows how LYTSwitch-4 can significantly simplify the design of offline, high-efficiency power factor corrected LED drivers and how to implement an EN 61000-3-compliant 2 Class C standard extremely high efficiency, high output voltage LED driver.