25W non-isolated LED driver for T8 lamp applications designed with LNK409EG, with circuit diagram, bill of materials, specifications

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Summary:

This document describes a non-isolated, power factor corrected, low THD, high efficiency LED driver that provides ~100 V, 250 mA drive for LED strings over an input voltage range of 180VAC to 265VAC.

LinkSwitch-PH uses advanced technology to achieve single-stage power factor corrected LED driver design and primary side constant current control in a cost-effective manner. The LinkSwitch-PH controller is ideal for LED driver applications with minimal external components. It provides control of the output current in the LED load without the need for an optocoupler.

The LinkSwitch-PH integrates a 725 V power MOSFET and controller in a single chip. The controller includes an oscillator, PWM (Pulse Width Modulation), 6 V regulator, overtemperature protection, frequency jitter, cycle-by-cycle current limit, leading edge blanking, and a charge controller for output CC (constant current) control. .

The LinkSwitch-PH also offers a range of other complex protection features, including automatic restart in the open loop, short circuit and output short of the control loop. Accurate hysteretic thermal shutdown ensures that the PCB temperature is within safe limits under all conditions.

The non-isolated, power factor-corrected, buck-boost design presented in this report shows how LinkSwitch-PH greatly simplifies the design of off-line, high-efficiency power factor-corrected LED drivers with very few component counts, and how to implement one Very high efficiency, high output voltage design that meets Class C harmonic current requirements.

This document contains LED driver specifications, schematics, PCB design drawings, bill of materials, conducted EMI measurements, thermal measurements, inductor specifications, and typical performance characteristics.

Display LED driver inside T8 tube

PCB assembly drawing of T8 25W buck-boost LED driver

Circuit Diagram of T8 25W Buck-Boost LED Driver

PCB layout for T8 25W buck-boost LED driver

List of components for the T8 25W buck-boost LED driver

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